Almost all devs will send you a digital poster, here are a few developers we have had luck with sending physical posters or promotional merchandise:
Survios (They have a swag shop now for posters)
VR Werx (Paranormal Activity)
Popstic (Hotel Transyvania)
Beast Pets (Sent stickers awhile back)
Again, almost any dev will send you a poster file though so you can fill your walls that way.