I like the tank, it reminds me of my first 20 gallon where I overstocked it with tetras haha.
I wouldn't go with 3 silver dollars since they like to school. I'd say either take them out or take out something else and bump their numbers upto at least 6. I have 11 and they're still skittish.
The pictus catfish, I'm not too sure on that. Some say they're a schooling fish, some say they get aggressive to other pictus when they get older, and some say they do just fine with one. All I know is that when I had my group of 4 juvenile pictus catfish they used every inch of my 55 and stressed out my other fish. 3 of them went back to the store and 1 evaded capture. The lone pictus has now mellowed out and isn't as boisterous as it was before which leads me to think that they aren't as active without other members of their kind. With only 2 I'd reckon that they won't be super active and might be ok for your tank.