Ok im trying to upload my racing skin to LFSW and it wont let me!! Could someone put it on LFSworld.com for me? Ill PM it to you so people wont take it and use it.
If you are saving in Photoshop, you can reduce the quality.
There's a slider on the right of the "Save for web" dialogue box, filesize is shown near the bottom somewhere. Not sure with other apps, but the option should be there somewhere (probably not in MS Paint though).