For myself, I often place the sea in the west as a concious decision (well, as far as sword-and-sorcery fantasy is concerned). I do this because, as a whole, it is easier to familiarize one's self in a setting that is oriented like Europe, which the fantasy theme usually emulates. From an artistic point of view, it is easier for the viewer to picture knights in shining armor fighting dragons and rescuing maidens when the map is oriented in a familiar fashion, particularly if the map is an decorative representation without many labels. Maps that orient themselves with the sea to the east tend to conjure up visions of dense cities crowded with Victorian buildings, new-world harbors choked with ships and skies thick with the smog of industrial steam engines. I've always noticed that, at least to me, the map instinctively creates a feeling between the "old" and the "new" by how it is oriented.

This is not to say that I believe that maps should be done in a certain way. The CG is full of examples of deviations from the "earth theme"; even my own fantasy world stretches off to the west with the sea in the east. The only orientation that I find difficult to deviate from is that it is COLD in the north and WARM in the south. I've experimented with placing a fantasy setting in the southern hemisphere and, being a child of the north and having never been south of the equator, it seemed too "different" to maintain the desired "feel" of the setting.