Thanks for the tips so far. Relative search seems like a good idea. I didn't even know it could be used for something other than text.
So this would be the correct procedure, right?:
1. Find a spot in-game and take note of which tiles are laid out in sequence.
2. Enter a tile editor, find those tiles and draw over them with a letter/number.
3. Run the game again and take note of the order of letters/numbers where the old graphics were.
4. Do a relative search for the string you got in the last step.
The graphics in Shadowrun seem pretty scrambled as far as finding/editing specific tiles goes, but it doesn't appear to be compressed. I guess finding specific tiles could be the hardest part now.
EDIT: Sorry, I think I misunderstood a bit. I'll try it this way anyway though just as a learning exercise.