This is the Island of Misfit Toys, except it's for coloring books (which probably means it's not the Island of Misfit Toys at all). Unlike the unfortunates in the Rudolph saga, our misfits aren't half as unlikely or uncategorizable as a Charlie-in-the-box or a cowboy who rides an ostrich. They're simply coloring books we don't carry, or from publishers we don't commonly stock.
Well, there are some oddballs in here to be sure, but there are plenty of children who'd be glad to color likenesses of the great composers, whereas finding a kid who wanted square wheels on his toy train would be considerably more difficult—such a contraption would be frustrating without any discernably redeeming attributes.
Have fun perusing, have fun coloring, and remember that everyone needs to be loved, even coloring books that are flung on the outer limits of human compassion, on that dust heap of confusion and coloring chaos known as Miscellaneous Coloring Books. Step carefully; you might need to avoid more than a couple ruined pencils or melted crayons.