There are many sources of suitable images for use as maps:, RPG PDFs, such as the Paizo Adventure Paths, or your own creations. You can use any JPG or PNG image as the background for a map. 

First, you create a new map in EpicTable via this button:


Then, you select a background image.


That's all there is to it. Your image will be distributed to the other participants in your game automatically. 

You'll want to watch the size of the images you use. I recommend staying under 2000x2000 and 96 dpi. That gives you a good sized encounter map without consuming a lot of memory and network bandwidth/transfer time. Depending on the source of your images, you may want to do some cropping and resizing before pulling the image into EpicTable. 

Notice that grids are drawn on the map by default. If your map image already has a grid on it, you can use the grid options in the ribbon menu shown above to change the size and offset of the grid. Some grids are irregular. For instance, they might not all be the same size (especially in older, hand-drawn maps), or they might be per-room instead of per-map grids. In this case, your best bet is to turn off EpicTable's grid and its Snap-to-Grid. Remember, part of EpicTable's philosophy is that, when all else fails, EpicTable can just be a table for you. It won't stop you from running your game, even when you're dealing with with less than ideal resources.