What is the etiquette on presenting work-in-progress that's mostly literature review in a conference talk in the humanities? Is it socially acceptable to present a conference paper which is not (yet) highly original research?

Being in the humanities, research requires much of literature reading rather than experimental or lab work. So, in a sense, it's inevitable that I need to take the existing literature as a starting point. 

Personally, I consider journals to be the proper place to disseminate original research. As a starting PhD student I am trying to participate in workshops and conferences as much as possible. 

Many times my presentations are work-in-progress and a personal synthesis of the vast amount of literature I have been processing. These presentations help me to make a "coherent story" of months of reading work. Making such a coherent story also helps me to orient my future research and accomplish intermediate research goals. Many times I submit an abstract to conferences to have some "external motivation" to finish some work before a certain deadline. Repeating this process, eventually, I am able to integrate these research goals to a higher plane where truly original research can be done.

Furthermore, I also consider conferences in a more broad sense. Rather than being a place to impress other people with your results, it's an opportunity to receive feedback and criticism. I also consider conferences as occasions where people with different backgrounds can meet each other, that is, meet each other qua human beings (not their research).

To formulate my story as a question: (a) How common is my vision of conferences? (b) Is it socially acceptable to present something which is derivative work-in-progress (and not yet revolutionary research?)
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.