What to do with portrait

Hey everyone,

I have a conundrum. My partner's (P) dad (D) died last year and as his only surviving family we tidied up his life. D had another son (M) who died at a tragically young age. Naturally, D was devastated and made his home into a shrine to the little one. He had a photograph of M blown up to oversized proportions (40" x 60" close up of M's face) and hung it front and centre in his living room. Now we own it.
We do not want to display it in our home. It's far, far too big and dominates every space it's in. Also P detests the actual photograph that D chose. I do, too. In the hundreds of photos I have seen of M he was an absolutely radiant, smiley child grinning his gorgeous little face off. D picked the one photograph of M where he is scowling and angry and P feels it does not represent M's true nature in any way.
And we already have other photographs of M on display in our house. Just this season I bought a beautiful frame and gave P his favourite pic of M for Christmas, which we gave pride of place until P moved it so that it is just out of eyeline because being reminded of M several times a day was upsetting him.
There is no-one else who would take this portrait (D lost contact with M's mother years ago) and we will never use it, but we also cannot bring ourselves to bring it to the dump and throw it in a skip. It is now leaning against a wall in our study/guest room, face side in, gathering dust.

Can anyone suggest a method of disposal that doesn't involve P psychologically throwing his baby brother in the trash?