Yeah I have managed to find some really awesome prompts to use by reverse engineering the whole /describe feature that midjourney has. I love some of the random stuff that's in there, like the "I can't believe how beautiful this is" is something that I've seen in a bunch of things -- enough to the point where people have started using it in their generative prompts now, haha.
I've had a lot of good luck also finding images that are close in style to what I'm trying to accomplish with my prompt on a site like pinterest and try to collect a few different examples of the same style/aesthetic. Then I'll work with the describe feature of that and generate some variations, til I can hone in on what I'm trying to ultimately achieve. It's pretty cool to be able to also see a bit behind the "thinking process", for lack of a better term, of what midjourney is doing to create these images. If you're in their discord, check out their channel called describe showcase I think is the name, or something to that extent -- it's got some interesting examples of people reverse engineering the whole prompting process.