1. A method, comprising: identifying, by a server, a boundary for a feature of an image, the feature corresponding to at least one tile of a tiling scheme for the image; storing, by the server, the feature in a cache when the feature is not already stored in the cache; tiling, by the server, the image according to the tiling scheme to produce at least one tile; for each tile corresponding to the feature, replacing a portion of the tile occupied by the feature with a replacement image for the tile; storing each tile in the cache that is not already stored in the cache; determining, based on the cache, that a communications device has the feature; and sending an indication of the feature to the communications device.