Hi GVA,
Are you traveling on Long Haul or Short Haul?
As crew, we get all sorts brought onboard, one of which being pictures/frames and the likes, and there seems to be no issues with it. As long as it does not class as "Oversize" or "Outsize" items, then bring it with you.
Depending on size, and if you want to, I would suggest politely asking the crew when you board, if it would be possible to store it in a wardrobe or the likes if it is of a size which may not fit easily into the overhead lockers. All our aircraft have wardrobes, some of them rather on the small size, and only numbering one, i.e. A319, but we will always do our best to look after fragile items.
If it is of a size that will fit in the overhead lockers, then I would advise you to wait till everyone is onboard and hand baggage is into the overhead lockers, then lat it across the top of the thinks that are already in there, so no one puts anything on top of it.
Hope it all works out for you!
Regards,