1,2,5,6 all have the uniting factor or the same frame. I don't really think most of them do look very cohesive. If you are talented at it you can make them appear coordinated. but i think it is not so easy, so i have saved some little cheats that will help. hold on, gotta dig!

see the same matt, same size, same frame and the wall acts like a frame too

wall is frame1 red frame to show center organize rest heading out from that one.same concept with frames, size and shape.see a large pic of the subject, all the smaller ones around it represent smaller parts of main one.

It helps for the art to be interesting in itself, not just in a bunch, and for it to mostly fill the frame -- otherwise it's just a pattern of frames and mats, in which case you might as well get one large abstract print instead.

Ugh! I am not good at that at all!! I have boxes of kids photos I want to hang in the upstairs hall but am paralyzed by the thought of arranging them!! My husband had to intervene to get the family photos onto the stairwell wall. (In chronological order) Lol!!
My walls have been generally bare for 4 years because I am so bad at this! :(

oh, you did not say what you were hanging, how about something like these?

hope they help!

https://www.houzz.com/magazine/an-insiders-guide-to-creating-the-perfect-gallery-wall-stsetivw-vs~54627547

https://www.houzz.com/magazine/a-gallery-wall-for-every-personality-stsetivw-vs~538039