I actually started thinking (oh wow this is forbittin) and came to a functional use for Mode 5.
Mode 5 could be used to simulate far distant BGs, yet... high-resolution :o. So non-pixelated BGs. HOWEVER, this only works with using IRQ, and you must make sure Layer 1 in the bottom half doesn't go above the virtual line that basically seperates the two modes.
Yes, I made an IRQ hack to do this. It's pretty simple. The top is Mode 5, the bottom is Mode 1. 'Letters' is on Layer 2 (Mode 5), as is the ground BG (Mode 1), I couldn't find better BGs. But I'd say, you could replace 'Letters' with clouds (did I mention you can make this layer 2 scroll slowest easily as well?), and you could replace the ground BG I used for the Mode 1 part with something... more fitting. So eh.
As for Layer 1... it should be obvious what's Layer 1. The lowest ground + steel blocks (Mode 1) and the high-resolution ground, Munchers and Dragon Coins (Mode 5).
Note: The only layer you're interacting with, is Layer 1 in Mode 1.
Don't follow "Find Roy's Dignity", my hack
. Because it's pretty outdated. <--------