Adding icons for the inventory must be done in a
.png format as it's the most accessible. It's recommended that you use at least
64x64 or a
128x128 image. Anything larger will pretty much be pointless since the inventory doesn't scale much larger.
Icons need to be placed inside of:
It is highly recommended that you compress your
.png file after it has been resized.
Check out PNG Gauntlet for resizing several images.