For more specific answers take a look at individual animals.
You could have dragons that glide with their skin flaps like flying squirrels instead of actually flying.
Burrowing dragons as I mentioned taking inspiration from the biology of badgers.
Dragons like tree frogs and chameleons with the ability to camouflage and have sticky pads on their feet.
Ice dragons with thick layers of fat. White scales for camouflage and countercurrent heat exchange system for the cold climate. Hey maybe you could have cuddling dragons.
I’d say have variations in sizes and environments. Some could reproduce like elephants and once in a long time and are going extinct. Others could be pests essentially. There is a lot of room for the differences you want.
With the whole alien element you could also add genetic influence. Maybe add genetic or tech enhancements that changed them.
From a world building perspective I’d suggest adding like evolutionary history. Maybe finding cave paintings or fossils.
Also there’s a documentary I’d like to recommend called ‘Alien Worlds’ which explores how life would evolve on different planets and it would be VERY VERY useful to you I believe.
I would suggest fleshing out what your planet is before focusing on your creatures. That would give you a base to build upon. It would be a much much more natural way to go about this.
You will find the previously mentioned documentary very helpful to do this.