I'd like it to look something like in the pictures below that look much more attractive

Well, if you want to do it like the pictures below, do it like the pictures below. Line everything up like they did. Done.

OTOH, you've got 10 pounds of prints on a 5 pound wall. It's just too much crammed together, especially low down on the table top.

I'd do a cluster of 3 in the center and then flow out in a single asymmetrical row on each side, one high behind the desk, one low toward the window.

Lay them on the floor and experiment.

Good idea but in the execution I see two problems.

1. In your inspiration photos the pictures/prints are aligned either horizontally or vertically. Or both.

2. Not enough white space between the prints.

Also, use the whole wall. Even behind the monitor.

Yes, do the whole wall. That's the best fix, because it will look intentionally haphazard and excessive, which is a nice look.

Get some brown paper and cut the size of each picture out. Then you can lay it out on the wall with tape until it pleases you. You might want to move the furniture away so you can reach the wall more easily. But one key is to establish vertical and or horizontal lines in the arrangement. I tried to cut and paste your pictures with a horizontal line and kept a few of the pictures also in line vertically with an even outside edge on both sides.

(I have a large gallery wall in my living room, because I just like all kinds of art, so trying to get it right can be frustrating.)

Your display would be helped tremendously if you would replace those heavy black frames with something much lighter and more narrow. As it is, they are swallowing up their pictures. The Mona Lisa, for example, loses her delicacy and meaning! There is also one, top row, second from left, looks a bit like a Matisse, which also needs a different frame plus a white mat.

Look at your sample pictures for pretty ways to frame and mat prints and paintings.

I think one of the difficulties here is that five out of your seven pictures are nearly the same size. How about more of a rounded arrangement?

The black frames with white matting are too prominent, and the very large piece on the right and very small piece in the first row seem anomalous. I've found the best way is to lay pieces out on the floor and evaluate the spacing, frames, size and the art itself for suitability. You might want to try different art or different frames from what you have.

The spacing between the are is visually important as well when hanging in a group

Consider shelving to make a nice horizontal base line

Or a row of shelving to display

the difference is, in all of the inspiration photos, there is nothing/ and no clutter, below the pictures. the pics take center stage. in yours you have that open cabinet w/all your stuff, and the loads of stuff to the left of it, plus your desk and stuff. it's too much stuff! the eye bounces around from stuff to stuff. find a closed storage console and find a home for everything else.

It's not just the way the pictures are hung it's all the "stuff" below and in the room. Too much, making a very unappealing busy area.

btw, this is one of the most difficult looks to pull off.

The more you can do to make the pictures "match", the easier it is to get a good look. I agree that the smallest and the largest pictures are the most different (size wise and also the narrow frames), and I'd remove them from the mix. Aligning the orientation (all portrait or all landscape) will also help. All-black frames will also help, maybe you can just spray paint the non-black ones.

First of all, it looks like you have a shiplap wall; a feature in itself that only needs one outstanding picture centered above the cabinet with perhaps a pair of candle sconces flanking it. This cabinet itself should also be centered on this wall. You are demanding too much multi-tasking of this tiny room, and it is not handling the job well. Try using some frosted film on the glass doors to help hide that clutter. If the office/computer table is also the dining table, it needs to be centered in the room as well. You many want to postpone this project until the "temporary" playroom can be moved to its permanent location, giving you room to do a better job. Groupings can be random, but that would include random sizes, and your's seem to be mostly the same size and all pretty large; variety is the spice of life!

I did not realize how many ideas influence hanging an art gallery. And all the points are good.

I wish I could just remove all the 'stuff' but my 5 year old loves her toys, so for now it will stay.

I hate the office desk and computer there, I will be trying to move it.

However, I do thing too the black frames are too heavy. I love the idea of hanging them over the entire wall. But then also the pint about shiplap being a feature that would require only one pice of art is also good.

Before I hung up this gallery, I did a lot of prep work. I cut the sizes of the frames out of brown craft paper and hung them on the wall to see how they would look. They did look much better than the picture frames themselves. So if identical brown paper frames look better, my conclusion would be that the colors of the picture frames are too many, or too heavy or both. I also agree that Matisse would need a white mat in the background and the largest picture needs to be replaced.

First I will try to make lighter frames and hang them in a rectangle all over the wall and then use a frosted film for toy cabinet. And I. will post a picture here.

And if that does not look nice I will just choose either 3 identical picture frames or 1 large picture over the cabinet.