I’m not very familiar with HTML5 and don’t know a tutorial to point at, but you should probably split up your problem in two steps:
- Obtaining the information from the JSON or XML map and determining where to draw which image.
- Being able to draw images at all.
If you’re getting only a white page, then you should start with the second step and make sure that you know how to render an image, before you try to look into parsing the JSON map.
You can also look at the multitude of frameworks available that have already implemented a convenience layer for rendering maps using HTML5. Either to use it directly or to learn from it.