The capability to rotate the label text is a nice to have. This allows to rotate the text at 90, 180 or 270 degree and have more flexibility on the way the maps looks like. On paper, the code could allow any angle as it creates a new image, write the text in left to right way then uses the imagerotate function to have the requested angle. Problem would only occurs for the alignment, but that's a trivial issue.

The provided patch only implements it for the element label, but it could easily be used for the labels too. Current configuration merges the rotation with the label location and stores everything in the label_location field. A better implementation would have its own label_rotation field in the DB.