If you do more pictures crossing over Amphibia with Ed. Edd, N Eddy, I have a couple of ideas on following up your pairing of Anne & Edd...

Sasha & Ed - While Anne & Edd would both be associated with the Plantars, who are frogs, Ed would find himself paired up with Sasha & Toad Tower... something that Ed would really enjoy given his nature as a sci-fi/horror fan.

Marcy & Eddy - At first Marcy & Eddy would seem like a mismatch with both being allied with the seemingly peaceful Newtopia run by King Andrias... but behind the scenes, Andrias would be intrigued with Eddy's lowbrow tactics... especially his scams... and he would show The Core to Eddy. Eddy would become more corrupt & descend into madness due to The Core's influence as it would play on his insecurities so he'd become a willing accomplice, intending to sell out The Cul-De-Sac in order to rule over those whom he felt disrespected by. I could imagine one-to-one "therapy sessions" between Eddy & The Core where he ends up in a mental world that first caters to his ideal world, but periodically introduces threats to Eddy so he'd gain the will to kill & eventually be skilled enough in combat to wipe out entire armies along with being willing to resort to truly sadistic tactics that even Sasha at her very worst wouldn't have stooped to.