OK so here's my suggestion, often when it comes to the image for a series the cover of the latest volume is used but I don't think this is a good idea because it may reveal something that spoils the plot.

An example is the series Eden no Ori if for example someone is just starting the series and they look at the image, which is the cover of volume nine they will see certain characters on the cover, but this is bad since it tells them that those characters will stay alive until volume nine which spoils the plot for a horror.

However I still like seeing these images so my suggestion is that when the page first comes up only the first volumes cover should be shown and a "more..." button like the one used for the recommendations or a "show all (some hidden)" button like for categories that will show the other images people have added should be available.

So please consider it and thanks for reading sorry it got so long though.