I expect many have had the same thoughts. I have just finished a quite large stationary engine and at +60kgs and more than 3' high it is a big lump!
And so the thought, "what do I do with it now" arose. Too big to put on a shelf and in any case being a static engine doesn't really do it justice. I didn't want to sell it but it is hard to display nicely when stationary so I decided to electrify the motion.
I had already had a wooden base made that it sits quite nicely on and being about 6" deep I thought I might get an electric motor to fit within this base.
I bought a Parvalux slow speed motor which runs at 75rpm. This was a bit too fast for what I had in mind plus I was a bit concerned that the torque to turn a large engine might be too much for a small electric motor so I fitted two bicycle sprockets which reduced the speed down to a stately 20rpm.
Once the flywheel was re-fitted the sprockets and chain are to a large degree hidden and the engine turns over quietly making a nice display item.