GitHub will host and preview your geojson files! Geomusings gives a good explanation of some pros and cons. Here is an example of a geojson stored on GitHub, then shared. GitHub takes care of the rendering via Mapbox.
Here I explain how to create a raster catalog in order to have a mosaic of a set of images. This way you can always add or change the images instead of just creating a static mosaic. I also find it much easier than dealing with the other ways of creating mosaic catalogs, etc.
One of the clients I work with utilizes unmanaged raster catalogs as part of their work flow. We manage over 20 raster catalogs with close to 4gb of imagery in both georeferenced jpgs and regular tifs. The imagery is black and white for the most part, some using the cg4 compression to get insanely small file sizes. We are now in the process of moving to the cloud, and they have chosen www.giscloud.com for their hosting, for reasons beyond the scope of this short post. The question: how to get these raster catalogs - which multiple images stitched together via the catalog with no data set so that they can overlap - into one image, small in file size and readable on the cloud.
This video shows the growth of urban infrastructure from 1850 (blue) through to the present (red). I utilized the time/timeslider/export video feature of ArcMap to produce the video. I suffered numerous crashes while attempting to utilize the time slider in a meaningful way into my actual production mxd, though I use several third party extensions which may interfere with native ArcMap features. Still I find this simple project mesmerizing.