Mecator Map Vector Template
This is a template for creating a world map in the Normal Mercator projection. It's an SVG which Inkscape will see as having three layers: a blue background, a graticule, and an empty layer in between. You can simply load it and start drawing. It should also be usable in any other program supporting SVG.
The graticule is drawn with 15° spacing, and covers 85° N to 85° S
This projection is good for a basic overview of a world and for laying out continents. Things get bigger further away from the equator, but generally stay the same shape (This is the same projection as those maps that show Greenland being as big as all of Africa)
If you prefer to work in a raster program, you can load it in Inkscape, and then export an empty template at whatever resolution you want. You may want to hide the background and/or adjust the style of the graticule first.