Do you have Mac OS X 10.5 (Leopard)?
If yes, here are a couple ways:
1) While in Finder, the quickest way is to select the picture and click the spacebar. This will open up QuickView so you can see the picture. (Leopard only)
2) Your images seem to be associated with Power Point. There's an application called Preview that can also be used to see pictures. While in Finder, select the picture. On the menu bar click File -> Get Info. In the Info Window, under Open with select Preview, then click the "Change All" button. Now, all the pictures of that type will open in Preview.
Also, if you need to learn some basics on Macs you can check out the following:
http://www.apple.com/findouthow/mac/