You might be able to find resin caves made to look like driftwood or rockwork at your lfs or online stores. I use one or more pieces of Simlawood / Simlastone in all 4 of my tanks - loaches, catfish, cichlids all love them.
Terracotta pots are fine but they look like plant pots to me, strangely enough. Functional but not very convincing or aesthetically pleasing. Like Purple says above of plastic pipe, you can hide them with plants or by siliconing other rocks and slate to them. Rocks will help to keep plastic pipes down, nothing worse for spooking catfish than finding their cave floating off!