The general concept of ifrit is that they are very similar to or are djinn, though they tend to be more hostile towards humans. However, in a modern Egyptian ethnography, I came across an interesting belief: ifrit are ghosts.
In Islam, the general interpretation of the theology is that upon death your spirit is immediately judged and taken to paradise or cast into hell. There are, in short, not supposed to be any such thing as ghosts. But the idea that ghosts exist is old as dirt, and it’s one that never seems to quite go away. The result is that the tradition underwent a modification. People still believed in ghosts, but when the local Imam came around asking questions, folks could simply refer to ghosts as a type of malicious djinn.
As a result, ifrit are often associated with abandoned (haunted) houses, murders, premature death, and the other paraphernalia of ghosts and hauntings. How you would like to use them is up to you; you could stick with the “evil djinn” angle, explore the ghost concept, or perhaps try for some synthesis of the two.