Cannot display still image on item display

We are having trouble getting a handle on item display on a new installation of Omeka 2.1.1.

The files_for_item() and item_image_gallery() methods appear to fire properly.

The appropriate URL appears in the href attached to the image, but the image
source will only display the default fallback-file.png image.

The fallback file image generally appears when you've uploaded a file, but Omeka was unable to generate a thumbnail for it.

What kind of image is this?

We have attempted several images (png and jpg), all under 1MB. Also, no errors have been reported in either Omeka or ImageMagick.

Would thumbnail images reside in
if they had been created by Imagemagick?

If that is right, then we have no thumbnails. We
are running a CentOS 6.4 32-bit server, and I
could not locate an Imagemagick package for it,
so I had to compile from source.

If IM is the problem, then I need a definitive way
to build it to support Omeka.

I think it's your ImageMagick install that's the problem. It looks like you might have it built, but without read and/or write support for many file formats (when building yourself, you'd have needed the -devel packages for things like libjpeg and libpng).

Does the CentOS 5.8 i386 RPM from (the first one listed) work on this system? That's probably the best available option.