The Monav data is currently used only for routing - it finds & describes a route between two given points. It can't be currently used for rendering the map layer (Monav can do that bud there is no interface for this available to third party applications like modRana).

Still, offline map rendering is also on the routemap, but i can't really say when it will become, as it is quite a bit more complex than offline routing.

By offline routing, you just find an optimal way on the route netowork, by offline map rendering, you have to draw all significant map features (routes, houses, water, labels) directly on the mobile device, at different scales, as quickly as possible. There are already some applications that can do that, such as the Monav client, Navit or the (closed source) Nokia maps. Unfortunately, none of them has an interface that modRana could use to ask for map pictures rendered by the application.

Also, offline map rendering would probably require a separate data package, as the the one optimized for routing (it has probably just routes and nothing more). This might not be that much of an issue as once the infrastructure for Monav routing data generation & distribution is in place, it could be also used for the offline map rendering data packs.

The most promising map rendering engine (from the modRana POV) is called Kothic and written in Python. I plan to investigate it soon.

tl;dr:
Offline map rendering is not yet supported, but planed.