Try to learn Snes asm and its hardware registers will help alot. I my self was a novice when I first stepped into rom hacking field, but after several years with learning, now I can solve almost game problems that I couldn't before. Just to encourage you.
For your question, try to use Geiger's Snes9X debugger. Then identify the graphic in question is which BG layer by pressing key 1, 2, 3,... The "what's used" button lets you know the BG's tileset, tilemap. Then press "Show Hex" --> Vram and jump to the address shown in "What's used".
You better read the game log and search for some keyword combos: $2116, $2118, $420B,...
From these information, you can search backward to get to the data you want.