Thanks for the suggestions, Mellow. I appreciate them. The back actually is painted with a high-gloss black paint. There's quite a bit of reflection in the photos, so it looks like you're seeing through the tank, but you're actually seeing what's across from the tank.
I agree with you about the branches. I have a box full of manzanita I'm not using, so I'll look for another good piece and stick it in there. Regarding the rocks, I think I'm going to stick with what's there (for now at least), but I'm going to keep my eyes open for good rock pieces at LFS's. Those are actually zebra rock, but I chose pieces with as little striation as possible. In a perfect world, Id be able to shell out $75 for ADA seiryu stone...
I agree about the hardware. I want a glass co2 indicator, and my grand plan is to swap out the reactor/powerhead and use a canister filter to distribute CO2. That would also eliminate the ugly HOB intake.
The guppies are endlers, and they're my babies. I'm only really interested in fish that I can breed. I'm considering putting scarlet badis, peacock gudgeons, or a dwarf gouramie in here (like sparkling or licorice gouramies). I'm not sure yet.