Brian, I owned and operated a gallery for some time. Let me tell you it is almost impossible to predict what will sell.
This is true, particularly on the internet. I have sold things I never though would sell, even while the pretty things languish unsold in a box. Been paying too much attention to the market.
Thing is, at least pre-Covid, while I never made remotely enough to make a living from it, sales were becoming a genuinely useful supplement to my very meager income. Then Covid basically wiped out the market for a year or two. It now seems to be slowly picking up again. But it also poisons one's enjoyment of making art.
I have been able to discern what won't sell on occasion. I showed the works by several artists that I knew were far too large or too expensive for the audience we had. My one Jewish studio partner painted these large mixed-media collage/paintings dealing with the Holocaust which might remind you of a cross between Robert Rauschenberg and Anselm Kiefer. He insisted on putting them in a holiday exhibition sale (Christmas) at which most of what sold were lovely ceramic, glass, and metals (jewelry). I am more than well-aware that the Nude is a hard sell... especially on the scale that I work. As the political spectrum around the world has shifted ever more toward the Conservative, it has become even more difficult to exhibit, let alone sell Nudes.
Yup, I don't see many nudes in galleries here either.
Obviously, if you are set upon making art to sell (nothing wrong with that) your best bets would be on flowers, still-life with attractive objects or vintage items that might draw on the sentiment of the buyers (old toys, games, etc...). Landscapes are also always a solid bet... although perhaps not landscapes with a pile of old porno mags.
Well, that's the whole problem. I also like landscapes, but I tend to like them just as they are. The other day an artist whose work I admire in a general sort of way posted photos of her plein air expedition on Instagram. She was painting a landscape very typical of what we see around here: rolling fields with electricity pylons. And I noted that in her painting, she had omitted the pylons!
Now that I would not easily do. I'm at a loss as to why people are so allergic to any signs of modernity in paintings. I grew up with those pylons and to me they have become very much a part of local landscapes. So have the stacks of porno magazines! Well, at least the ubiquitous rubbish, or car wrecks, or ruined buildings, the stands of non-indigenous eucalyptus trees, etc. I love pictures of grimy, smoky industrial areas, trains and trucks, and so on. These things are the very heartbeat of civilization, though I also like them abandoned and slowly sinking back into nature. (One day, when I'm rich, I'll make a pilgrimage to Chernobyl!)
Anyway, such things are not without market either; we have a local artist here who does very well for himself painting scenes from our run-down rural towns. He has a particular penchant for abandoned swimming pools, full of dirty water and rubbish.
Still, the local market tends to prefer pretty things. My problem with the suburbs is that they are neither pretty nor beautifully ugly. They tend to be just bland and boring. There are sometimes attractive gardens, but around here, because of rampant crime, people live behind high walls and electric fences, so you don't get to see the gardens!
Still, there's much to see and paint, some of it pretty, some of it beautifully grim and ugly. I have set myself the task of discovering it for a while.