You should create a page somewhere with your banners on, whether its for affiliates or just people that would
like to use your banners, or perhaps you like swapping banners with relevant sites.
I usually get a
468 x 60 banner
120 x 120 banner (suitable for navigation menus)
The more choices you have with different colour schemes, the more likely a webdesigner will use them, as
sometimes we don't want to carry ugly banners or banners that go against our colour schemes.