Once you have a UV map texture for an object, you can resize up or down to your hearts content as long as, like TDK man says, you keep the same aspect.
One simple rule with computers and compression, the smaller the initial uncompressed file, the smaller it will be compressed. So reducing your images to 256 colour, or less
, will always reduce overheads. Common sense when you think about it really.
I still remember working with 8,16 and 32! colour palettes. Amazing what you can do with em really, well in Dpaint 4 lol
. I used to reduce all my textures to minimum 256 colour when I coded in DB classic. Don't bother so much nowadays, but that's only because I am spoiled by modern hardware!
Edit - Oh! I almost forgot, somebody said 640x480, 256 colour textures = ugly. I personally think running your 3d app in 320x200 looks uber cool and really retro! if you have never tried it, have a look lol, fair enough, it's not what you want these days, but if you want a retro look what could be better! It's like running your game in dosbox emulator
http://s6.bitefight.org/c.php?uid=103081