The too-thick plaster mix has actually added some character to the castings, with parts of the piping looking slightly decayed and rotten.
Finally, here's a shot of the markers with a GZG light vacc-suited explorer and a Xenomorph, plus a smaller QRF alien creature.
I'll mix up some thinner plaster for the next lot of casting, and will probably add some black poster paint. This will produce a darker finish that won't show up the chips in the paint in case they get knocked. The moulds will need a small amount of trimming to ensure the plaster can reach all the pipework. Time to start work on the hive!