I've always thought engine kits are interesting. There seems to be more pre World War II subjects. Engines and Things has a lot of WW II engines in 1:48 that are intended to be AM for aircraft kits but I suppose one could scratch build an engine stand. I'd also be interested in turbines. Other than the rare aircraft kit that has them (the Hobbyboss F-105 has a J75) I'm not aware of any source of turbine engines.