Natural Earth is a public domain map dataset available at 1:10m, 1:50m, and 1:110 million scales. Featuring tightly integrated vector and raster data, with Natural Earth you can make a variety of visually pleasing, well-crafted maps with cartography or GIS software.
250m True Marble global dataset. This is a low resolution version of the full 15m product. Two types of files are available for download: GeoTIFF and PNG.