They're good covers but I do not think this is the best idea, namely because these covers do not represent the original work of the author who would use them. I guess this applies for any sort of stock cover, but overall, a cover should reflect the story it's for, and therefore should be unique to it. It should therefore not be reused for other works, as it risks undermining both the stories its used for, along with the cover itself.
However, the one of the bottom left corner is simple and ambiguous enough that it could be used for any romantic story while still reflecting its contents.
TLDR: Your artwork is great, but most of those covers should not be reused for other stories.