I'm no minimalist, but that is all too much stuff and some of the things don't really complement each other. I would either do art or stuff above the cabinets and not both.

Sorry either the stuff all over the top or the art but not both. Really art is best when hung to have the center of the art at eye level so those would be too high as show them so find a wall. I am a firm believer in less is more in decor so one piece on each cabi net would be all I would do Infact since you like a bit of eye clutter why not so a"gallery" wall on that large wall opposite the mirror.

the reflection in the mirror looks like you have a blank wall on the other side of the room, why not group all your framed art together for a statement and make the singular pieces a separate display.

I like a layered look, but this feels like a thrift store! It is is too croweded and seems like some nice pieces of art and objects are getting cluttered together. What other walls can you hang the art on?

I would remove the mirror and use that space for a nice collection of art.

You are standing on the other side of the room to see art above a cupboard. The art is small enough where you're standing no one can really get a focused look at it. What's the point? If you want something over there I would keep the stuff and remove the art to a place it can be enjoyed. But to your question yes all frames should be the height of the mirror or all frames a bit above. The right side looks sleek and cohesive the left not. Arrange all frames so the overall balance matches.

As mentioned by others, you have too many small items on display. I suggest you group some pictures in similar frames above the buffet and perhaps a small pottery collection on one tall cabinet and a plant on the other.

With the style of your furnishings and the brushed finish on the hardware, your choice of a brass framed mirror seems to totally wrong for the room.

No pictures there on either side. None.