Creating fantasy / interactive maps is quite easy with leaflet and some other (free) tools.
Have a look at this:

Pedro's Tech Mumblings: Zoomable image with Leaflet (see maptiler for creating the zoomable map, it's easy to use)

You can use whatever image you want, and then you can add some markers using this syntax:

var marker1 = L.marker([-70.0,-70.0]).addTo(map);
marker1.bindPopup("<b>My Mark</b><br>blablabla.");

I managed to do it, I just had to make some tests for adding the markers at the right place. It even works on mobile devices such as phones, tablets...