This room is bursting with creativity!!!! I love love love your lamp guitar stand (where'd you get that?!) and your wife's pet portraits are amazing!

Okay so the biggest thing that jumps out to me are the brown blinds. They're fighting with the brown wood floor and the brown wood desk. Are you open to replacing them? Maybe you could just pull them open, and put some fabric blinds around them so that you have darkness when you need it, and then your wife can have natural light when she paints.

Next, yes to more black items to tie the room together. I like this

After that, maybe you can find some more metal things to echo your AMAZING guitar stand lamp? Search online for "industrial" design. Your wife's stool might already be considered a little industrial. Here's a fun update to your light switches you could check out.

What about cable management? Your lights are cool but the wires underneath are distracting. Try something like this. Maybe you can put the guitar lamp in front of it.

One goal to keep in mind for balancing a room is symmetry. You and your wife each have a desk, that's symmetry. They're against the same wall, cool, can you move things around so that they feel symmetrical a little more?