i whould suggest something (dunno if it was already suggested) about the minimap. It is slow and heavy and is full of details. Yesteday i've tryed to take the minimap and convert it into png 256 colors. I didn't see any change and the size of the pic is strongly lesser.
Here an example of a map with lots of colors. (i've take a swamp that have much colors)
-----Png Normal (41,0 kb) --------------- Png 256 (19,8 kb)------

I didn't tryed GIF 256, but is the same. They keep Trasparency to put patterns if you need.
If you wanna be more cool, you could create your own Palette and all the minimap don't need more than 256 colors.
I repeat, i dunno if someone of you already suggested this, but i know there was a thread somewhere. I didn't found it, sorry.
Any extension you use (gif-png-jpg-bmp-tif..or more) i think you could use the 256 colors of Photoshop. They cut a lot of size and dont ruin anything because the minimap don't use so many colors.