What is "teaser image"? It is asked by a journal in a revision request. The only info that I was able to find is at this link:
Please identify a teaser image from your manuscript that may be used in the abstract book as part of the OnlinePlus program and send this information via email to the publication's administrator. Note that failure to include this information will cause delay in posting/processing your manuscript for publication.
They want you to select either a figure or possibly a more creative rendering of your research, for the purpose described in your quote. Imagine your article was going to be a book, they want you to pick an image for the cover.
If you don't have eye catching data, try to figure out the most effective way to visually describe your theoretical work, and produce an image of that.