The fact that the 'maze' image on the home page rotates suggests use of a rotation cipher. There may be other treatments either before or after using the rotation cipher, so if you try all 25 and nothing, see if doing another transformation before or after does anything. For example...
The fact that the Tweetie image with the hand-drawn icons that also appear in the lights on the home page after twisting on iOS are Reversed (mirror-image) suggests that the letters/numbers need to be reversed. This might involve conversion to binary and doing a logical not of all bits, then converting back to ASCII/UTF-8 (or, as they are in pairs, perhaps UTF-16). Or maybe converting to binary and then reversing the order before converting back to one of the mentioned character encodings. Or maybe reversing each pair. Dunno.
Also, does anyone know of a code that involves both numbers and letters, but is case-insensitive? A simple caesar cipher usually just operates on the alphabet and not numbers. Maybe the rotation is still the way to go, but the numbers mixed in are either red herrings or, extracted, provide a separate clue from the letters themselves.
Just some thoughts.