Limoncello has a fair amount of sugar, but the beer yeast will ferment that. It's really just going to be that lemon zest flavor that you'll be adding for the most part, and none of the sweetness. There are quite a few styles that would work well with that kind of straightforward citrus note. The ones that come to mind for me are Pale Ale/IPA, American Wheat or Blonde Ale, Witbier, and Saison.
Which style to choose depends on your preference, really. When I want to accentuate an ingredient, I tend to brew a "milder" version of whatever style I'm going for. For an IPA, I'd use less late/dry hops to let the limoncello fill that role. In a Wit, I'd use just a touch of coriander and ferment a couple of degrees cooler to keep a lower level of yeast expression. Or I'd choose a style like American Wheat where the base beer is pretty straightforward and will get out of the way of the ingredient you're adding.