The best way to illustrate abstract concepts is with abstract art. Instead of clear-cut objects, vague patterns capture the feel of fluid thoughts and concepts better. This event invitation template from Canva is an excellent example.
Use this green layout as is, or pick a different background from Canva's extensive design library. There are over a million free and premium images to choose from. Simply drag and drop into the layout. You can also edit the font style and colors to match your new background. Design is easier when you're using Canva, so go ahead and explore!