Sprites
The list basically speaks for itself here. Unfortunately, none of them are indexed, but i'm not that good. I guess you'll index them as you use them and since I did a test to see how fast I could index and pallette swap and it took me less than 20 seconds, I dount it will matter. Please note: Every sprite is split up individually, if you are after sprite SHEETS, then see the Useful Links section and select Spriters-Resource. Credits to the owner of PLDH.net

1st Generation
Every Pokemon Sprite from Red, Blue, Green and Yellow. Including Backsprites.

2nd Generation
Every Gold and Silver Sprite, plus BS. Crystal Sprites are in the Animated Sprites section.

3rd Generation
All of the Ruby, Sapphire (The same), Emerald, Fire Red and Leaf Green Sprites (FR and LG are the same). Oh yeah and BS ;).

4th Generation
Diamond and Pearl, Platinum, Second Frame Platinum, Heart Gold and Soul Silver, HGSS Second Frame, Female for all of them and Backsprites.

5th Generation
All Black and White Sprites, plus the BS and Females. (BW Animations in the Animated Sprites Section.)

Mystery Dungeon Portraits
The Portrait of Every Pokemon up to the Shaymin.

Mystery Dungeon
Unfortunately, Only the Front Sprite, but still one of the biggest collection of PMD Sprites i've seen as it goes all the way up to Shaymin.

Ranger
The Front Sprite of every Pokemon from Ranger, up to Shaymin.

Dreamworld Art
Custom Art of every pokemon. Not Hacking Related.

Sugimori Art
Custom Sugimori Art of every Pokemon to date. Not Hacking Related.