Hi George,
If you have edited the photo in another program, it might just have the generic icon. Most programs give you the option to save with an icon Preview, so check the prefs of the other programs.
If you navigate through the Finder, make sure you have "column view" set and make sure you have View>show view options (in the menu bar), check off "show icon preview"
If you still can't view the icon preview for some photos you can use third party programs.
there are many third party programs that can do this for you. One is called Pic2Icon
Pic2Icon
Another one is a contextual menu item called QuickImageCM.
QuickImageCM
check out that page because there are some other useful contextual menu items that I use all the time.