Vista - Windows Media Center and image files

I've had Vista Home Premium installed on my desktop PC for over a year now,
but I never used Windows Media Center until recently and noticed this problem
when I purchased a Media Center Extender. After choosing the folders (music,
video and image) that I wanted in my WMC library (on BOTH my desktop PC AND
Media Center Extender), only my image files do not appear in the libraries.
Under "Picture Library" (again, on both units), all folders and sub-folders
which I selected are shown but contain no "items". The files which I desire
to view are .jpg, .jpeg, .gif, and .bmp formats and I have converted some
back and forth between formats to see if that changed anything. Can anyone
steer me in the right direction on this? Any help would be greatly
appreciated.