I have a variety of what looks like variables names such as _LOGOUT and _YOURHOME instead of what I'm assuming should be images and buttons. So far it's only on the admin pages and not on the site that a non-adming user would see, since I've added a couple blocks and the site looks fine.

I got interrupted many times while ftp'ing XOOPS to my site and re-started several times, guessing at what point and what file I was at when I got disconnected. So I'm assuming I'm missing some kind of mapping file or properties file that maps variables to images.

Likely files in language/english folder are missing.

You probably need to upload all the files again, you might miss other files which could make your system unstable. Find another FTP client or upload the tar.gz or zip file directly and unzipped the file on your server.

Thanks, that mostly did it, you were right. The only remaining ones I've found after that so far are a _PREFERENCES and _CLOSE in the block that pops up when you mouseover the blocks that I've added, such as polls and news.

Both of those are defined in language/english/global.php

If the langauge files were missing when you did the install, you might need to update the modules (or even do a re-install) to get all the language definitions to take effect. I think that some of the definitions get stored in the database, rather than being picked up dynamically from the language file.