Just as you enjoy having a furnished house, your betta appreciates a little pizazz in her tank. Plus, you'd probably enjoy watching her more in a spiffy tank setup. Building her an imaginative tank doesn't take much -- a few plants, decorations and substrate usually brings it all together.
Your little betta loves plants, and in her mind, the more the merrier, so get a little creative and set her up with a forest-themed tank. Opt for live plants over fake ones -- they look more realistic and your betta enjoys them more. Add a variety of sizes and colors to bring out a true forest feel. Place small plants near the front of the tank and larger ones in back. Arrange a few pieces of driftwood in your betta's aquarium, laying small pieces along the substrate and standing larger, branching pieces up vertically to mimic the appearance of trees. Purchase some moss and attach it to the branches of the driftwood. Eventually, the moss will grow along the branches and make for a green canopy. You can also attach moss at the base of the make-believe tree and allow it to creep up the trunk. Remember to leave enough open space for your betta to swim.
If you want something easy to set up and visually appealing, consider a desert-themed tank for your betta. This theme calls for sand substrate instead of gravel. Of course, having nothing but sand in your betta's tank won't make her too happy, and it's not very creative, so plop a little oasis in there. Set an unpainted and unglazed base of a terracotta pot in the middle of your betta's tank. Layer the bottom with blue sand so it looks as if a body of water is running through the desert. Surround the base with live plants and other decorations to bring the oasis to life. One idea includes setting rocks behind the terracotta base and then attaching moss to the rocks. The moss creates a little overhang of green growth overtop the blue sand.
Your betta might not be able to play video games, watch movies and television shows or read books, but there's no reason she can't experience pop-culture themes while swimming around. Many pet stores and online aquarium stores sell pop-culture decoration kits, but typically only from wildly popular movies and television shows. You can create your own decorations from aquarium-safe materials, such as PVC pipe and interlocking plastic bricks.
If you want to house multiple bettas with your current betta, consider a divided tank. Divided tanks essentially split your aquarium into multiple compartments with the use of store-bought or custom-made dividers -- each compartment can be home to one betta. To take the creative idea a little further, make each compartment a different theme, but stick with the same substrate throughout. If you're attempting a natural theme, be aware that dividers do not lend well to that setup.
Store-bought dividers typically consist of plastic or glass sheets -- make sure they has holes -- that fit into brackets. Custom-made dividers can consist of several aquarium-safe materials, but an effective and cheap method fits plastic canvas into plastic report holders. Plenty of online sources offer in-depth instructions and other ideas for custom-made dividers.