I have created toobar and want to have ICON or Picture on It. Since the picture size being too large it is not shown as complete on Toolbar command button.

I tried to convert it to icon also, but the ICOn is becomes too small and is not explictly visible.

What should I use BMP/JPECG/PNG/GIG/ Or Icon for Toolbar Command Button ?
what Picture size should be kept ?
Which is the best site to create Icons

Regards