Any pedals that are a distinctive part of one (or many) of their songs that you could do? If there’s a really great tune of theirs that has a really distinctive phaser part for example, you could do that with a graphic that thematically fits that song.
Sorry I can’t be of more help with the specifics in that regard, but I have made some pedals as gifts for musicians, and stuff like that always goes over really well because of the feeling of a collaborative connection it gives— it’s like their work of art is directly inspiring a different work of art that they can then use to create a new work of art.
I’m seeing Pond in November (never seen them before since they rarely play the US outside of Festival dates— last time I had an opportunity to see them was like 2012 or 2013, but it was a school night and I was just a wee lad) and I’m hoping to build a simple custom pedal each for Jay, Nick, and Shiny Joe, and a noise synth for Jamie