Okay, my funny bone is pretty seriously tickled here. This is utterly charming and so well-conceived. I heartily approve of any idea that means we get multiple drawings from you instead of just one. The more, the merrier. And I echo all the other commenters who delight in the cracked, grainy photo album. Perfect presentation.
My favorite panels are Harry menacing a freshly showered Snape with his mad towel skillz, Snape fishing Harry's Y-fronts out of a pensieve (I have no idea what's going on there, but it still cracks my shit up), Harry desecrating Snape's potions lab with his nail polish and his sandwich crumbs, and then, of course, the glimpse of them as jowly old dudes in lurve (and how happy do Snape's bristly eyebrows make me?). Okay, I'm also extremely fond of unshaven, grotty-looking, bed-head Snape and doofus-y, besotted Harry, who is clearly much too awake and gazing raptly at Snape like a smitten chipmunk. Obviously, it's love. In all cases, their expressions are priceless.
And Snape actually gets to be happy for once. Believe me, I'll vote for that.
Thank you for lavishing so much care and bringing so much delight. <3