The latest version of StepmaniaX uses the Stepmania 3.9 alpha 7 release for its backgrounds, animations, etc. etc. However, I cannot find 3.9 alpha 7 anywhere on the net, and it doesn't seem to work with any of the newer releases, or with 3.0 final.

Is there anywhere to download the older releases of Stepmania?

Not sure what you mean, but V. 5 in the usual places comes complete with all the files necessary.