People tend to love cheap and simple stuff, YCHs are popular because aside from being themed (which is perfect for seasonal stuff like Halloween or Xmas), it gives a good idea of consistency that stays cute and having examples that people can exactly expect at the low price, plus it saves time from people from thinking up poses etc and they can just simply link you their OCs that fits a YCH
And back when I offered multiple options, icons/headshots were my most popular option for the same reason above. I know chibis are popular for this too, but mine didn't do fairly well as I didn't have many good examples with them haha.
And here's to add another point: Have as many examples!! Again, having consistency and a visible idea of what to expect of your style/art is important! Commission is a luxury, and people are extremely careful with what they want to spend on--no matter how low or attractive a price is--so they'd like to minimize the risk of getting a comm they don't envisioned as much as possible by this. Just writing what you can/cant draw is great, but a picture is worth thousands of words! It's useful for buyers that are seeking specific styles but I personally would buy a commission if I see a style that fits a specific OC among various that I have, if this helps!
Edit: To add some of my personal experience, I once offered a 2$~5$ sketch commission in the past, and a 20$ fully rendered commission as of recent. Despite what I've been saying on "people prefer cheaper stuff", the 5$ one actually sold horribly...yet the 20$ has been pretty successful? You could argue that its the time gap between my style's improvement, but I feel like one huge factor is that I provided way, way more consistent examples for the latter, whereas my sketch comm had like 1-3 examples and they were all sloppy and inconsistent? That's at least what I assumed! But this kinda shows that underpricing yourself is not the solution to everything. Adding with all the risk-aversing factor I mentioned earlier, you definitely should be the judge to your own price, and most importantly, show as much confidence in what you're offering!
And extra tips: (for commissions in general cases)
- Put your price range in your commission title if possible! Its really the fastest way to "market" your commission
- If you're going to offer shading options like "flat / simple shaded / detailed shading" and the likes, that's 100% fine but from what I experienced second-handedly, most people tend to usually? pick the cheapest option for this, even if its only flat colors. I personally suggest not opting for shading options unless you have drastic difference between various shading styles for this reason (again, more examples are the key!), but its really all up to you if you think its worth it to offer them!
- When participating in LF threads, if the OP offers multiple OCs or an entire folder as an option; I will always mention which OC(s) from that folder that I'm interested in drawing the most. (e.g. "Your characters are so cool! I'm especially interested in drawing <name X> and <name Y>") I'm not sure if it increases the chances but it can definitely help narrowing down options for the OP and I like showing some interest on which of the potential customers' OCs fits my style the most!
But other than that, sadly the simplest answer is to participate in those LF threads, and ofc keep bumping your commission thread! The climb to reach any potential customers is the hardest part in opening commissions, I feel that (I was once in your place as well and frankly can't remember or even know how I even managed to reach some customers in the first place haha)
Good luck!