I love the themes, but none of them hit the spot for me just right. My favorite for now is Ayu but the orange bugs me a bit. It would be nice to be able to choose a basic theme like Ayu and select the accent color from a hex code, slider, etc.
The way Slack handles themes is brilliant—they have presets but also let you customize your own theme by selecting the color for each UI element. This level of customization would be ideal and really make Bear feel like home.