[Oh yes, surely it must be the light. When Elizabeth looks again, the symbols haven't moved at all-- no, this time they change entirely. One by one, each time she averts her gaze, she'll find more have transformed to look like the Eye of Horus when she returns to it. In fact, by the time she looks at the wall as a whole again she'll find every symbol transformed into the same infamous eye.
She'll begin to hear it then, archaic whispers, unintelligible muttering on the wind and then another voice emerging as a culmination from them all:]

“WELL LOOK WHO IT IS.”

[One of the Eye of Horus-- huh, when did that one become bigger than the rest-- suddenly opens into a real eye.]

“LIZZY THE TREASURE HUNTER! I WONDERED when we'd MEET face to FACE.”

[Bill peels himself off the wall, his camouflaged form taking back on its usual gold luster, keeping a small bit of the Horus makeup for show.]

“How's it HANGIN'? UNCOVER any more SECRETS, since we last SPOKE?”