Ideal Image Sizes?

What would you say the ideal of mix of image sizes (width, height and flesize) would be for the following types of sites..

1) TGP Galleries
2) Free sites
3) AEN Sites
4) Paysites

Ive been looking around at a few places this morning and it really doesnt look like people use a 'standard' for anything.

Whats your preference for each and why?

Regards,

Lee

I only do TGPs and Free Sites to generate traffic... so high quality is something I have to forfeit.

I make the maximum width or height 600 pixels. any smaller than that, and a lot of link lists won't list them, any bigger, and you're gonna get a crazy bandwidth bill.