Hello and welcome to reefcentral! I will do my best to assist you. Now, as you know, a 34 gallon tank isn't very large, (but also not considered "nano"), however, it is the perfect size for a nice assortment of fish. First off, can you tell me what trigger you currently have in the tank? Unfortunately, because of its capability of reaching a rather large size as an adult, you won't be able to keep it comfortably in there forever. I'm not positive of the growth rate of triggers though, so it may be okay for a while.
So, considering you're going to keep the trigger for a while, I wouldn't get a dwarf lion unless you sacrifice either the small puffer, or dwarf angel. Reason being: I used to have a small toby puffer in a tank that size, then added a dwarf lion and within minutes of it being in the tank, the puffer had knipped at all of its long spines and split them off of its back completely! It not only stressed out the lion, but also made it look rather unattractice and scrawny. Any of the small toby puffers would be fine in your tank, such as the valantini puffer, or white spotted puffer. Just be sure you don't house any ornamental shrimp with them, as it'll soon become a rather expensive treat!
You could house any of the dwarf angels in there too, remember the one-to-a-tank rule though, too. A favorite among many is the flame angel, eiblii angel, and coral beauty angel. Did you have any particular ones in mind?
In order to let your bio-logical filter keep up with the load you would be putting on it, I would stock your tank 1-2 fish at a time over the period of a week or two. Remember too that it's best to add aggressive fish last, to let the more timid ones establish their own territories and feel comfortable in their new home.
If it's not too late to take back the trigger, as it will outgrow the tank soon, you could certainly add more fish. Just remember though that if you would decided to take the dwarf lion route that they can and will swallow smaller fish whole, so be careful on your selection!
I hope I was of some help to you!
Neil