Like the others above have said, just do what you want. But are we talking about some sort of client/contract situation here? I would expect the contract to at least outline what the things you can/can't do for miscellaneous art that arises while working on said contract.
Depends on the context of the situation in regards to pressure, but usually the answer is yes. If it is just self imposed pressure to post, then yeah experiment away. If it is a deadline for a commission, I think that experimentation is good with each client; to a point. There are some that want what they want, when they want it, and want no deviation from the concept. But all in all I think experimentation is a must, to grow and perform as an artist