Initially, they didn’t become visible at all for me. Then I did this ritual here Belial's Gateway Symbols with Belial and then the second time through (I didn’t see anything the first 3 days, but I rested and went back several days later like it says) I saw him in the aluminum foil. He took the shape of a friendly dragon, and then he shape shifted before my eyes into the shape of a scary gargoyle. Then he shifted back after I asked him to and for a moment I could actually see both forms at the same time. Honestly it took me a while to get used to Belial’s shape shifting.
I second the don’t take pictures without permission from the spirit, and that applies to them, offerings to the spirit and alters. They can break your camera.