Just finished creating a gallery mockup in Photoshop.
Dimensions of psd.file: 5000 x 4000px
RGB – 8 Bit
You have 4 walls to choose from.
1 smart object (red)
just click on it
create a new layer on top
fill this layer with your poster (embedded)
and you are good to go!
Export your poster as .png in with your dimensions.
File Size: 396,6 MB (sorry for the size)
Location: my Google Drive