I think my tank looks bad, any suggestion?

This was my first tank, and it really needs a makeover, but I’m not sure where to start. I'd like it to look more natural. Does anyone have suggestions?

I’d like to incorporate sand since it’s better for my corydoras, but I don’t want to replace all the substrate so I was thinking about a sand path or just a section of sand. I have shrimp in the tank, and I feel like they would make the process of draining and taking everything out a huge pain.