fish with german blue ram

I'd suggest at least 5 more yoyo loaches and otos, they prefer being in groups. Even if they don't necessarily school they seem more comfortable and active with more of their kind around. My otos are very active, and bold (they like to play "dart under/around the siphon" x.x)! I think the betta's fearless personality is rubbing off on them >.>.
No real suggestions on other species though sorry, though i will say "stay away from shrimp", i think your rams and loaches may eat them. Maybe look into a peaceful schooling fish for some added mid/upper tank movement.

I would avoid the shark.

My German Blue rams hate my SAE. They always chase him off, no matter what. If he wasn't so docile I would be afraid of the combo.

Well you could always get some Tetra's or Rasbora's. Not sure what you keep your temperature at. And yes that shark will eventually get a little to big for them. I've had yo-yo loaches with shrimp and they were just fine. A few little ones will get picked off but mine were fine. And I've got shrimp in most every tank I have including my ram tanks and from time to time they will eat one but for the most part the shrimp are fine and help keep the tank clean.

Personally i would do some schooling fish such as the Cardinal tetra and the Rummynose tetra. Both look good schooling together and there colors aren't as vibrant to take away from the colors of the GBR. They also both are able to handle the higher temps. Mid level fish as to stay out of the way of the GBR's. MAybe even look at a Powder Blue gourami as they tend to stay to the Top level of the tank. Just ensure enough food makes it to the bottom.