Are you having issues uploading TIF files?
If you try to upload a TIFF file and it fails, you should check the projection of the source TIFF file to start. Currently, Map Mavin only accepts a GeoTIFF. So you will need to make sure the TIFF file has a projection which makes it a GeoTIFF. If the TIFF file has no projection and only a TFW (TIFF World File), it will not load correctly.