Thanks, but I still don't quite understand it. I understand how the graphics are stored. For example, a 2BPP image, here is one byte of it:

AABBCCDD

Where A-D are different pixels. But what I don't understand is how this translates into planes in FEIDIAN. I figured out that to dump 2BPP linear just like Tile Molester, I can use "AAAABBBB" in both planes. But this doesn't make sense to me. It seems like it should go by pairs of two somehow, because each pixel takes up 2 bits..

As I understand each letter specifies a different byte, and repeats of the same letter represent different bits of the same byte.
(so you should end up with 8 repetitions of each letter).

So you have:
AAAABBBB
AAAABBBB

What that means is that the byte A represents the left 4 pixels of plane 1 (since it has the first 4 repetitions of "A"), and the left 4 pixels of plane 2 (since it has the last 4 repetitions of "A").
Byte B represents the right 4 pixels of both.

I don't suppose anyone here still has copies of the now unavailable tile definition files, now would you?