I prefer no background because the color of my wall gives the tank a "frosted" look.You can get a dark background? That would help.
I'm happy with just a school of 10 barbs because I also want variety, I would feed them more than just algae but that should be their main source of food IMO and because I do not have a lot of it I would not feel comfortable housing these fish in my tank.You could still add more cherry barbs if you wanted. 12-15 would be fine since they're the only school.
And you can still add otos or a BN if you wanted. You should be feeding them veggies anyway, rather than making them rely on algae in your tank only. If you feed them veggies daily, you don't need algae in your tank.
That is a fine list, but you could still add a bottom dweller centerpiece. Since you don't want a ram, how about a pair of peacock gudgeons?If I got rid of the guppies could I add a school of green neon tetras? So: 1x DG, 7x Corydoras Aeneus, 10x Cherry Barbs, 8x Green Neon Tetra? Is that to many mid dweller schooling fish, or could I add something more?