Well, I can comment on the modern bits, although it sounds like that might not be what you're interested in.

Locations and architecture

Well their depiction of modern Cairo is pretty fake. http://4.bp.blogspot.com/-YLLcOCru440/UYSpk5F1nNI/AAAAAAAAAkU/8GH_xawVb84/s1600/cairo.png

This picture shows what's pretty clearly supposed to be Fatimid (Islamic) Cairo within viewing distance of the Pyramids which loom large over the city. While you might be able to theoretically see the Pyramids from the Citadel (and even in the 20's I'm pretty sure the haze would make it impossible, as it currently is today) they would appear very small indeed on the horizon given that they're miles away on the far side of the Nile. I don't know when this photo dates from but I'm pretty sure those are the Pyramids as viewed from the Citadel in the horizon on the square fourth from left, which shows you what I mean.

Several scenes are also set at the "Museum of Antiquities". There was a bureau of antiquities but I'm pretty sure this is supposed to represent the Egyptian Museum in Cairo opened in 1902. However, it looks nothing like the one in the film.

You can see in images like this which seem to show British tommys in a building likewise situated in Islamic Cairo: http://2.bp.blogspot.com/_3H1dWtzmZYU/TAj-fjUhiUI/AAAAAAAACiI/YM5owx8R9c4/s1600/Die_Mumie_The_Mummy_14.jpg

That's pretty unlikely. Most of the expatriates were set up in Garden City or Zamalek, then as now. Shepheard's hotel would have been a more likely place for them to have been than anywhere within sight of the old city.

I'm not sure if the "Terrence Bey" character is supposed to be the curator of the museum or merely Evie's boss, but by the 1920s there were Egyptians in senior positions in Egypt's museums, most notably Ahmed Kamal who was an assistant curator at the Egyptian Museum. Though Kamal died in 1924 (the film is set in 1925) and there was a dearth of Egyptian Egyptologists for another decade or so, as I understand it, I'll give it a pass for "realism". The being said, European administrators would still have been the norm.

Clothing wise, the film was shot in Morocco and the clothing on the "Egyptian" peasants looks like they just grabbed modern Moroccan extras. Those thick brown woolen robes are more typical of north-west Africa (Tunisia, Algeria, Morocco) than an Egyptian peasant' galabiya, which tends to be thinner. Also if you had a bunch of zombified Cairenes in the 1920s I'm not sure they were all peasants and not more guys in suits and fezzes, but again, I'll let that slide. For more on Egyptology in Egypt in the 19th/20th centuries see Whose Pharaohs? by Donald Malcolm Reid. It's less about Howard Carver expedition-type stuff and more about the structure and politics of Europeans and Egyptians in the museum bureaucracy and the place of Egyptology and ancient Egyptian hisotry in modern Egyptian nationalism, identity, and colonial politics.