[Shinichi]

1- Is it possible to have altrenating backgrounds for a forum?
2- How large would a BG image have to be if I simply wanted a picture on a side of the forum?

[Ruffian]

1-I'm not sure what you mean. Do you mean a randomly generated image that changes constantly?
2-The side of the image would be the size of the image... unless you mean two images, in which case one's size will not affect the other as it can overlap it.

[Brandon2KO]

I can do the side part easily rotating maybe im not sure

[RXS]

1) So like if you go to a specific forum, then the background changes? Because that's an option in forums. If you want images changing every so often, you might need to create a .gif file.

2) You can position a background image.

background-position:POSITION;

You can POSITION to whatever position you want. For instance, top right, bottom left, etc etc.

[Shinichi]

I just realized the position thing. And I mean altrenating every page load, if possible.