Hi!

I'm new to graphic design, and don't have much experience. I mostly do work for myself and for fun, sometimes post on people's requests, and now I want to upgrade my profile ^^ So I would like to know what dimensions are best for banners and backgrounds for my profile. I couldn't find it anywhere :/

Anyway, thanks in advance

your screen resolution would be good dimensions for the background

Thanks any suggestions on the banner size?

as a background you can use a pattern (Repeat-x Repeat-y or repeat all)
That way your background will fit on every screen resolutions.
Making a background the size of your resolution will looks ugly with people using higher resolutions screens.