That a pretty nice sized tank, not really big but alot larger than the 10g and 20g highs a lot of people have.
Don't get a pleco they poop everywhere, I love mine but... he poops everywhere, like double all the other fish combined lol.
Maybe some rainbow fish? They will take up most of your space tho, but they are very pretty and very fun to watch. I have 9 turquoise rainbows in my 150, just try to get more females than males, I think they usually breed them this way I got lucky and my LFS
had way more females than males but its hard to tell them apart and I didn't really know until I bought them.