The main skill of the designer is to be able to tell a story
Just like it is with arts compositions, photo series and other art works, what you can hear about them in general is that they all try to tell you a story. This is not a story per se, not like a fairy tale or something with a definite beginning and ending.
It’s rather about the depth of a photo, when you either see something is happening which can give way to your imagination or the overall feel and atmosphere of the photo is what makes you think.
When it comes to web design, the situation is more or less the same. You ought to find a theme or a core inspiration for yourself. Try to read articles with artists or even fashion designers and hear them talk about their inspiration and the stories they want to tell with their compositions.
Look for themes, let that be based on a story, on a painting, on a photo or on a natural scenery. Look for photos similar to your theme to further help you with your composition and finally you have the story to tell.