Designs whose pictures are lost (Ckole, Elementality, Kluffer, Mikesee) have been omitted. Links within categories are in chronological order.
Tailgate to front (over reclined front seats)
Shaped 2x4 and plywood with PVC legs (convertible, can be used with front seats upright), by BikeZen
Plywood and pine with pipe legs, by NismoGriff
1x2, plywood, table legs, and PVC by Inmyelemet
Modular, 3/4" plywood and 2x3s, finished with foam and custom cover, by Tseydel
2x4s, 3/4" plywood, and PVC (based on Bike Zen's) by E:ndiana
Plywood and steel pipe, by Dirkbeaulieu
2x4s, plywood, and PVC, by Vermonter
Modular, wood and PVC, by Tedsti
Tailgate to back of front seats
PVC pipe, by Pookster [plans]
2x4 and pine, by Will_morgan
Pine box frame and particleboard with metal crosspiece, by Gaily
Variation on Gaily's, with extension for open tailgate, by Ramblerdan
1x4 and plywood with PVC legs, by Twilightzero
1x4 and plywood with iron pipe legs, by Sarahp
Plywood with pipe legs, with extension over fully reclined rear seats, by TCW
2x2 and plywood, with commercial table for back end, by Jojo
2x4 and plywood with iron pipe legs, by Eventure
PVC frame and plywood, half- or full-width, by Strawintogold
PVC frame and plywood, variation on the PookSter platform, by Lefty
PVC frame by Nbpguy
PVC and plywood, by Zinguy
2x4, plywood, and steel pipe, shallow (8 1/2" rear, 11" front) to allow access to the rear side storage areas, by Soulcall
Pine board and plywood with iron pipe legs and hinged front section, by Sandiegotaylor
2x4s, 3/4" plywood, piano hinge and table legs, by Neilp
Steel cage, by Pokeyzilla
Bi-level, plywood and 2x6s, by Mikem
Wood box frame, with extensions, by Rodsnhawgs
Plywood, modular, by BlakeVW
3/4" plywood, modular (similar to BlakeVW's), by Bentanks
Wood slats, with some metal parts, by Nubsy1
Modular, plywood and 2x4, by Benlavallee
Longitudinally folding (half or full width) 2x4 and 1x4 pine, can be used outside the vehicle as a bench, by Plankwalk
Metal drawer baskets and plywood, by Elefante
Cot-style, folding, wood, by Nightrider
Wood with pipe legs, folds for storage or transport, by Twitchy411
Plywood, 2x4s and PVC, by Treybrad
All-plywood with piano hinges and drawers, by CosmoSwiller [external site]
Aluminum square tube and Hurriguard-brand plastic panels, by Hot_Karl
Plywood, modular, by Hotelement
Wood, incorporates spare tire well, by Lambertdarr2 (view pictures in reverse order)
Plywood and steel legs, with front extension, by Spikeselby
Tailgate to back of front seats, modular/convertible
1x3 and 2x2 wood, by CerealBox
PVC and cedar slats, by Ray Al
Plywood, by Night Hawk E Camper
Wood slats and PVC legs, based on CerealBox's design, by BPD
Half width, with extension to dashboard on passenger's side
1x4 and plywood with iron pipe legs, by Roadtriperic
1x3 and plywood, by MMs2011E (with video and link to external PDFs)
Half width, tailgate to back of front seat, modular/convertible
Hollow-core door with PVC legs, by Arm2008
Aluminum and wood, mounted to exposed rear-seat frame, by Ray Al
Tailgate to top of reclined front-seat backs
1x4, pine, and angle iron, by Paulj
1x4 and plywood with iron pipe legs, by TheTimeTravelers
1x4 and plywood with iron pipe legs, by Rishio
Variation on Rishio's, with extension for open tailgate, by AppleAficionado
Plywood and metal angle with Ikea legs, by Goofcat
Plywood with metal angle, by Flyazureair
Plywood with PVC legs, by Mehlhorn
Pine board with PVC legs, by Staisey
Plywood and PVC, modular (platform or just a shelf behind the rear seats), by BreE
Particleboard and PVC (longitudinally folding), by D.Cool
Wood and aluminum pipe, by Kcousins
Plywood & PVC, modular, by Jazz82482
Plywood with PVC legs and wood frame, carpeted, by M Silver [external link]
3/4-depth structure, laterally and longitudinally folding
PVC and plywood, by Dangerjack
Shelf/half platform combo
Plywood and rear seat bases, by MTBecamper77 (external link)
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Corrections or amendations: PM Ramblerdan
Tailgate to front (over reclined front seats)
Shaped 2x4 and plywood with PVC legs (convertible, can be used with front seats upright), by BikeZen
Plywood and pine with pipe legs, by NismoGriff
1x2, plywood, table legs, and PVC by Inmyelemet
Modular, 3/4" plywood and 2x3s, finished with foam and custom cover, by Tseydel
2x4s, 3/4" plywood, and PVC (based on Bike Zen's) by E:ndiana
Plywood and steel pipe, by Dirkbeaulieu
2x4s, plywood, and PVC, by Vermonter
Modular, wood and PVC, by Tedsti
Tailgate to back of front seats
PVC pipe, by Pookster [plans]
2x4 and pine, by Will_morgan
Pine box frame and particleboard with metal crosspiece, by Gaily
Variation on Gaily's, with extension for open tailgate, by Ramblerdan
1x4 and plywood with PVC legs, by Twilightzero
1x4 and plywood with iron pipe legs, by Sarahp
Plywood with pipe legs, with extension over fully reclined rear seats, by TCW
2x2 and plywood, with commercial table for back end, by Jojo
2x4 and plywood with iron pipe legs, by Eventure
PVC frame and plywood, half- or full-width, by Strawintogold
PVC frame and plywood, variation on the PookSter platform, by Lefty
PVC frame by Nbpguy
PVC and plywood, by Zinguy
2x4, plywood, and steel pipe, shallow (8 1/2" rear, 11" front) to allow access to the rear side storage areas, by Soulcall
Pine board and plywood with iron pipe legs and hinged front section, by Sandiegotaylor
2x4s, 3/4" plywood, piano hinge and table legs, by Neilp
Steel cage, by Pokeyzilla
Bi-level, plywood and 2x6s, by Mikem
Wood box frame, with extensions, by Rodsnhawgs
Plywood, modular, by BlakeVW
3/4" plywood, modular (similar to BlakeVW's), by Bentanks
Wood slats, with some metal parts, by Nubsy1
Modular, plywood and 2x4, by Benlavallee
Longitudinally folding (half or full width) 2x4 and 1x4 pine, can be used outside the vehicle as a bench, by Plankwalk
Metal drawer baskets and plywood, by Elefante
Cot-style, folding, wood, by Nightrider
Wood with pipe legs, folds for storage or transport, by Twitchy411
Plywood, 2x4s and PVC, by Treybrad
All-plywood with piano hinges and drawers, by CosmoSwiller [external site]
Aluminum square tube and Hurriguard-brand plastic panels, by Hot_Karl
Plywood, modular, by Hotelement
Wood, incorporates spare tire well, by Lambertdarr2 (view pictures in reverse order)
Plywood and steel legs, with front extension, by Spikeselby
Tailgate to back of front seats, modular/convertible
1x3 and 2x2 wood, by CerealBox
PVC and cedar slats, by Ray Al
Plywood, by Night Hawk E Camper
Wood slats and PVC legs, based on CerealBox's design, by BPD
Half width, with extension to dashboard on passenger's side
1x4 and plywood with iron pipe legs, by Roadtriperic
1x3 and plywood, by MMs2011E (with video and link to external PDFs)
Half width, tailgate to back of front seat, modular/convertible
Hollow-core door with PVC legs, by Arm2008
Aluminum and wood, mounted to exposed rear-seat frame, by Ray Al
Tailgate to top of reclined front-seat backs
1x4, pine, and angle iron, by Paulj
1x4 and plywood with iron pipe legs, by TheTimeTravelers
1x4 and plywood with iron pipe legs, by Rishio
Variation on Rishio's, with extension for open tailgate, by AppleAficionado
Plywood and metal angle with Ikea legs, by Goofcat
Plywood with metal angle, by Flyazureair
Plywood with PVC legs, by Mehlhorn
Pine board with PVC legs, by Staisey
Plywood and PVC, modular (platform or just a shelf behind the rear seats), by BreE
Particleboard and PVC (longitudinally folding), by D.Cool
Wood and aluminum pipe, by Kcousins
Plywood & PVC, modular, by Jazz82482
Plywood with PVC legs and wood frame, carpeted, by M Silver [external link]
3/4-depth structure, laterally and longitudinally folding
PVC and plywood, by Dangerjack
Shelf/half platform combo
Plywood and rear seat bases, by MTBecamper77 (external link)
______________________________________________
Corrections or amendations: PM Ramblerdan