If I make the small image a .gif, will it still pick up the medium and large images if they're .jpgs? Or do they all need to be the same such as all .gifs or all jpgs?

I'm asking rather than just doing it, because I'm having reload issues and I'll probably never know that it didn't work until hours of effort has been put into it. I haven't had the greatest of luck experimenting around with things like that.

Thanks,
Kelly