http://osdmsoftware.googlepages.com/pocketpicture
or
http://www.xnpocket.org/
I use PocketPictureSI more for drawing and effects much like photoshop, but free!
I use xnpocket as my default for opening jpegs and gifs does a nice basic job for what you are asking in the op, plus makes showing pics from a folder so much easier! (also free)...