Do things that are commercial I was told. Look at the market and decide where you want to position yourself. Thats not for me. I am certainly not doing sensible. Eat my art as Alan Partridge might say.
These are not your comic fantasy creatures, or your manga battlers. Often they are some apsect of nature or our ourselves personified. Take care they bite.
A proffesional artist should create a series to show they are serious about something. But as Ratty might say, "Hang Spring cleaning, I dont see why there are any rules to this. So take that art world".