Hiya
To decrease the kb or the dimensions of a picture you need software that can do it.. I use paint shop pro 8 or the software that came with my camera. There is also a post in the photo galery about photo resizers that you can download from the internet to use.
Regarding the changing avatars - like picture shows.. there is a post, again in the photo gallery giving instructions. Again you need specific software to make one. Alternatively get in touch with Gareth and he might have time to make you one (he made mine for me lol)
Hope this helps some xx
Helen x