You may use any video footage for tiles. Please just keep in mind that if you intend at some moment of your video mosaic to show a zoomed cell for a full screen, it will be a good idea, that the video clip used for this mosaic cell has the same resolution as your future mosaic video.

For example, if you are going to make video mosaic for Full HD resolution display, and if you want to finish your video mosaic clip with final zoom in to the central cell of mosaic you'll need to fill the central cell with video clip in Full HD resolution. If you fill the cell with lower resolution video the end of yout mosaic clip will be blurred because of video up-scaling.