I hate just having the dirt. Some of my plants have pretty big pots now, and i would like to dress them up a bit. Would mulch promote mold?

Mulch can promote pests so isn't the best idea to use for indoor plants. A better idea is to use Spanish moss or decorative pebbles.

I prefer to use pebbles or even sand to dress up the tops of my pots, with the added bonus of retaining moisture and discouraging fungus gnats.

I use Spanish moss, it helps maintain the moisture in the soil.

I always use those river rocks in my bigger plants.....I think they were 97 cents a bag at walmart.