I have just found about stripgenerator.com from a tweet from @mrsenorhill (who learned about it from @josepicardo)
The online application is very simple and super easy to use. It doesn’t have many options (in terms of characters, templates, etc.) but I think that’s the beauty of it. Students (or teachers) using it for storytelling would not be spending hours browsing thousands of characters and background but (hopefully) just be inspired by the simplicity of it and spend more time on the language, the story. I agree with @mrsenorhill that the built in social capabilities are very handy for story creators to share their work.