Hi everybody. The aspiring game designer strikes again. Did you notice, that D&D did not manage to create a coherent set of symbols for the 8 schools of magic in 33 (!!) years, while Harry Potter fans have kickass sigils for Hufflepuff and Slithering since day one? My very first installment on the DMs Guild aims to remedy this shortcoming. Check it out, it’s free! Magic School Symbols
You’re probably right about the ‘coherent’ part, but D&D does actually have symbols for the schools of magic (see PHB 3.5, p 169). They pop up occasionally in the latest remake in various illustrations of magic items.
No reason they can’t be improved upon, of course.
Hope this helps with your card design project!