These days, many editors require photographic projects, a unifying theme to the images, some times even to the point of accepting weaker images just because they fit with the theme, even when the photographer may well have dozens of stronger images at home which will remain unseen because they aren't part of a project.
I certainly understand why an editor would do this. The publication looks better when all the images from one photographer are from a single project or at least theme. The ability to produce dozens of strong images on a single topic says a lot about the abilities of the photographer.
I would point out however that many of our greatest photographers did not work this way much or all of the time. Pepper # 30 is much loved. Ever see Peppers 1 - 29. I suppose you could include Edward Weston's other vegetable images but I have only ever seen fewer than a dozen vegetable images from him - ie. good enough to be published. That won't even get you in the door of Lenswork, for example.
I love 'Chez Mondrian' by Kertesz, but I have not seen any of his other images that remotely look like this image or are on the same theme. Instead his publications show a wide variety of subjects from street photography to 'shot from my window' type work to people.
Other well known photographers definitely did projects or worked within themes. Edward Weston could and has done entire books from nudes. Others did or do nothing but projects.
I guess that for those who don't photograph to an agenda or do projects, the hope would be to come up with enough really strong images that they can do a book, though even there publishers like themes so one may be self publishing which basically won't work if you don't have a reputation which you aren't going to get if you don't get published. Hmmm.
There's always the readers pages in photo magazines but as that generally results in only a few images at best, it really tends to reinforce the message 'these were the only good images'. Black and White magazine from U.S.A. accepts small portfolios of images - 8 if I remember rightly, while Black and White Photography (U.K.) published my badlands images a few years ago based on a submission of only a dozen or so images - but all one theme.
Has anyone had success getting published or shown in galleries without a strong theme or without a specific project?
I wonder what editors think about this - since clearly their needs are not necessarily ours, entirely reasonably.