I use natural items, such as rocks and driftwood... But I use the most practical shapes and stack them in the most practical ways... so in the end it's not realy all that "natural". Terra Cotta pots are very cheap and practical too but I try to only use them as needed for breeding pairs.
Here is a pic of one of my tanks as an example:
This is cut rock from a landscaping yard that is cut into brick like shapes and slate like shapes... I had to put the pot in this tank to give the female Trimac somewhere to hide from the male.
Edit/PS - Wow, I didn't realize how terrible that pic was when looking at the thumbnail before I posted it... sorry...
Here is a pic of one of my tanks as an example:

This is cut rock from a landscaping yard that is cut into brick like shapes and slate like shapes... I had to put the pot in this tank to give the female Trimac somewhere to hide from the male.
Edit/PS - Wow, I didn't realize how terrible that pic was when looking at the thumbnail before I posted it... sorry...