One of my first major edits was to create a new fireplace for the 2.5D tiles. I felt like I needed one that would fit into the normal sized walls, while the one that was released with them looks like it is two stories tall.
After that, one of the things I find that keeps maps interesting is to have a lot of variety in the contents of shelves and containers. When using Parallax maps, there is no downside like there is when using tile sets.
This guide shows step-by-step how I built my fireplace, as well as some other edits to get you started.
And here is also a short video of the process to create open filled barrels.
Zyph's Game Design 