Mm, yes, balancing is far from perfect at the moment. I tweaked scoring until it felt good and produced reasonable layouts, but wasn't very concerned with the relative scores between tiles. The wall in particular is difficult because it blocks growth in a direction but still needs to feel rewarding to place.
I'm definitely interested in experimenting with more complicated mechanics, but for a short web game without a tutorial it might be difficult to pull off without confusing new players. I'd definitely add a combo catalog if this were to become a full release!
Thanks for your suggestions!