Yes, this topic should be stickied ideally.
This is a big mod I am doing, perhaps an "ultimate" mod for the GP2x; using a MKII GP2x. Lots of work on this yet to do, only just got the system functional and working fine.
It looks bigger than it is from the pics.
I am using a PSone screen (40% bigger than the GP2x).
Better buttons and better laid out.
Prettier case (will be when done, WIP at moment, and working on the guts; ugly at the moment though).
Using C-cell batteries, 5500mAh NiMH cells. Lots of battery life.
Rotating screen, whilst using same controls (useful for some MAME games).
Normal sized digital D-pad joystick, far better control expected.
55mm speakers for far richer audio quality.
Reset facility and battery recharging facility (external plug).
Here are some teaser WIP pics, lots of work to do yet.
If you want to see the WIP guide and keep up on the project progress, please view this topic on BenHeck:
HERE
I have some other minor GP2x mods on my sig too.