I think having the outlines on the counters and cabinets works nicely with the style of the sprites. However, you don't need outlines on the floor tiles, in my opinion. I often use "are objects overlapping?" to determine whether to have lineart somewhere or not. When there is no overlap, outlines are often unneeded and needlessly distracting. Of course, style is even more important, but I think this method might work for you in this case.