Displaying cover art images in MP3 files?

So I got one of these this Christmas, and want to add cover art to my MP3 library so it will display on-screen during playback. It seems simple, but I'm having some issues. In short, MP3 files created with cover images in Musicmatch seem to work. But existing files I add an image to with a tagging utility do not display the image on the Archos player.

I'm sure many here have in-depth knowledge of all things ID3v2. Any advice would be appreciated.

I assume said tagging utility doesn't have an in depth tag browser. I would start by comparing a working file with a non-working one and seeing what the differences are.

So what you're saying is you've got two programs... Musicmatch, and some unnamed tagger.

Both have options to add pictures? Musicmatch works and the other one doesn't?

My guess is this:

Each of those two programs adds the pictures in a different way obviously, and I'm guessing that one of them isn't even using a proper ID3V2 tag, it's just appending the image to the end of the file. I've seen that sort of thing before, where a program just adds nonstandard crap at the end of an MP3 file and expects playback software to sort it out.

The trick is figuring out which one is which, and more importantly, which of the two that your player is expecting to display.

Tagger = Zortam MP3 Media Studio 5.85

Yeah, I was sure I had found the problem when I saw that the working file stores its image in the "other" field, not "front cover". However, copying or moving the image to "other" on test files has not worked.
But that does make me consider whether my testing has been sufficiently controlled. I'm going to try making modifications to copies of the working file and see what happens.