Cut a groove in a length of 50 x 50mm wood. Screw the wood to the wall as a picture shelf. The groove will locate the bottom edges of the mounted / framed pictures & stop them slipping. For framing, clip frames can be found quite cheaply, even with real glass. Maybe have another shelf 600mm above the first, etc.
You can change the pictures round whenever you feel like it.
Cut a groove in a length of 50 x 50mm wood. Screw the wood to the wall as a picture shelf. The groove will locate the bottom edges of the mounted / framed pictures & stop them slipping. For framing, clip frames can be found quite cheaply, even with real glass. Maybe have another shelf 600mm above the first, etc.
You can change the pictures round whenever you feel like it.