I'm not a dev, so I can't outright give you a solution. However, I can provide you with some insight as to where I think the problem might be, if you would be so kind as to look a little further into the matter.
Any incredible owner can tell you that barely any apps out there get along with the internal storage of the device (mnt/emmc). From what I have heard, most apps use the default android media scanning method which just scans "mnt/sdcard". By changing this to "mnt" instead, it should scan "mnt/emmc" as well. I don't know how you are going about checking for tag info or album artwork, so this may or may not help at all. I just think it's weird that the widget can pick up the artist and song title, but not the artwork.
I also have album thumbs located in "emmc/Android/data/com.android.providers.media/albumthumbs" if that helps at all.