What is the etiquette on presenting work-in-progress that's mostly literature review in a conference talk in the humanities?
Although I'm in the social sciences rather than in the humanities, I'll give a general response:

"Socially acceptable" is an odd question. I understand that you are asking about if people who attend your session might find your presentation appropriate or not. However, academic conferences are peer-reviewed. That means that before youre presentation can be presented to an audience, it is evaluated not only by the conference committee, but by two or more subject experts. So, if your presentation is acceptable to the committee and to the peer-reviewers, then I expect that that answers your question--yes, they have approved it for presentation before an audience. (Of course, and especially if you are only submitting an abstract for consideration, you must be explicit that your final presention would be of a literature review.) If they don't accept it, then no--though their rejection might not be because it is a literature review per se--it could be for many other reasons.

Also, note that what is acceptable for one conference might not be acceptable for another, and indeed, what is acceptable for one conference one year might not be acceptable another year (since you often have different evaluators). Only by actually submitting would you know.

So, in short, submit it for peer-review and then you'll get your answer. You don't need to worry about the audience; the peer-reviewers are there to protect them from inappropriate material.