It's going to be difficult to remove these lines completely, however there is an approach which can reduce them to an extent. The result is not perfect though.
I used GIMP and the G'MIC plugin's Fourier Transform filter to suppress the stripe pattern, but if you can find a Fourier Transform plugin* for Photoshop, you could also do something similar.
Actually this kind of problem is really hard to solve in Photoshop without affecting the quality but I will try to do my best.
If we are talking about only this picture
At first duplicte your original layer to use in further or prevent any accident.
Change mode to lab color to get different color space in Photoshop
Make sure that you selected all channels ...
This can easily be automated in Photoshop.
Before you begin make sure all your 4 x 6 images are in one folder, and take a note of the folder location. You may wish to split up the job using several different folders, as this will generate lots of new documents, especially if you have 300 photos!
Click File > Automate > Contact Sheet II
Choose the folder ...
My answer is similar to Tetsujin's method, but created non-destructively using a Threshold adjustment layer, grouped with the image layer, then the group set to "Multiply" mode. A noise filter can then be applied to a purple background Smart Object.
For greater similarity to your examples, it's probably best to start off with a photograph taken with low ...
From original image - yeah, don't ask ;)
Add adjustment layer - Threshold
Add layer mask [reveal all].
Select all, copy, alt/click mask, paste.
Invert. This should leave the black but make all the white transparent.
Add new layer, drop it behind.
Use paint bucket with flat purple.
Filter > Noise > Add Noise
Not claiming it's used (see NOTE1), but the result resembles how BW photos in the past came out from photographic printing. Here's described one old process for hobbyists http://www.alternativephotography.com/an-introduction-to-the-gum-bichromate-process/ One makes his own photosensitive paper which will take ink differently depending on how strongly it's ...
The technique is called solarization. It can be achieved in a b/w photo dark room, when the printing paper is exposed and already in the developing fluid for a bit, the room lighting is quickly turned on and off, so light areas get exposure too. Durations of exposure and development can be varied to achieve a variation of different results.
Photoshop does ...
Apparently this artwork is called Rimova and was made by Nicholas Law. Most of his art seems to have the same look so I'm sure that he has spent a lot of time refining this technique. A similar result is probably more than a few clicks away.
Obviously I can't tell you exactly how this was made, but I'll try to give you some inspiration for further ...
Since you've added "Photo-editing" as the tag I'll attempt an answer, but you can forget Illustrator. It's no good for editing photos which are raster images.
It's pretty easy to create similar effects in Photoshop, or other similar raster image editors.
In Photoshop you could take a regular photo, turn it into a Smart Object, then apply an Iris Blur to it,...
Compositing can be more difficult than it may appear. At least if you are seeking a believable composite. I think your sample is okay, but not great. Some angles aren't really correct and the shadowing/lighting could be a bit better. But it's not a "bad" composite overall.
You can easily find thousands of examples related to poor compositing.
Just a ...
It's going to be difficult to obtain a clean selection using the kind of selection tools you have already tried. In cases such as this the human eye and manual editing skills can trump anything automated.
Don't mess around with manual erasing. You can get much cleaner results by creating a vector mask manually, using the Pen Tool to create the curves.
You can use luminance noise reduction, but the overall result will be to lose detail.
If that is part of a much larger image, sharpening or using high-pass on the result might regain some apparent edge detail, but on that small segment it's hard to tell.
Quick bluff through Photoshop, no re-sharpening as I don't know what needs to be sharpened from so ...
You can use actions to automate things.
Basically it works like this:
Open the Actions panel.
Click the Create new set button to create a new set to contain your action(s), give it a name and click OK.
Click the Create new action button to create a new action, give it a name and click Record. Now Photoshop records everything you do. There are lots of ...
Have a few separate complete pieces of proper plants or leafs as images with transparent background. Have several copies in different sizes and rotation angles (see NOTE1). Place them until you have enough, do not clip a maze, because the edges would be wrong.
You may need also pieces which are squeezed vertically or horizontally to simulate watching ...