If you aren't a designer, find a designer who can advise you how to do this important step. Make it a game. Allow yourself 30K in images per page. GIF files are most commonly used on the Internet. It won't affect the image much visually, but the JPG compression may make your image file size smaller.
Smaller files load faster on the screen.
Test your files on several different computers and browsers. Using several smaller images may create other problems. To arrange them as you want, you will have to use tables. Finally , be sure to use hyperlinked text navigation aids on your pages. From a design standpoint it may look less polished, however, it's user-friendly.