I have been making my own reverbs recently through recording impulse responses.
I've tried recording various spaces with different reverbs. Its fun to experiment with other things too for example solids. I've tried to get impulse responses from radiators, pianos, plates etc.
You can record them using either room sweeps (try REW's ) to a sharp sound such as a balloon pop. You can get some interesting sounds. The next thing is then to select a dry sound and experiment with them. Ableton live is easy to use with them. So is Reaper which is a great low cost DAW. I highly recommend it.