I recently heard about #Isgaudrim-Dragons from its founder thirteenth-sanction, and after a brief look through its gallery I've seen that it gathers work of a rather high quality. The group is solely for original works, ie no fan art, which leads to it having a good variety of styles.
If you're interested in taking a look, the group is here: [link]
And if you'd like to submit to the group, take a look at their rules here: [link]
The group is free to join, and even if you don't want to, I suggest watching it for the good artwork that it collects.