Picdex

A note: while some of these sprites do have white backgrounds, quite a few are transparent. I put them against white so they're easier to see.

Red, Green, Blue, and Yellow

Green Red/Blue Yellow RGBY Back

Gold, Silver, and Crystal

Gold Gold Shiny Silver Silver Shiny
Crystal Crystal Shiny GSC Back GSC Shiny Back

Ruby, Sapphire, Emerald, FireRed, and LeafGreen

Ruby/Sapphire Ruby/Sapphire Shiny Ruby/Sapphire Back Ruby/Sapphire Shiny Back Emerald Emerald Animated
FireRed/LeafGreen FireRed/LeafGreen Shiny RSEFRLG Mini RSEFRLG Mini Animated

Diamond and Pearl

Diamond/Pearl (Platinum Pose 2) Diamond/Pearl Shiny (Platinum Pose 2) Diamond/Pearl Pose 2 (Platinum Pose 1) Diamond/Pearl Shiny Pose 2 (Platinum Pose 1)
Diamond/Pearl/Platinum Back Diamond/Pearl/Platinum Shiny Back Platinum Back Pose 2 Platinum Shiny Back Pose 2