One of the biggest things I think D&D Beyond is lagging behind on is mapping, especially when it comes to PbP.  Maybe this is the programmer in me thinking, but if PbP could integrate mapping and some continuity of "turns", PbP could be so much better.  So we're left with working with a blog editor toolbar, which fortunately allows some interaction with the html.

Is anyone doing anything clever with images?  I had this idea if you could stack images on top of another from this Stack Overflow post. 

Pretty cool, huh?  I got it working in JSFiddle first, then basically just inlined all the style.  The basic structure is 

<p style="position: relative; top: 0; left: 0;">
<img style="position: relative; top: 0; left: 0;" src="{map url}" />
<img style="position: absolute; top: {pixels from top}px; left: {pixels from left}px; border: {color} solid 1px" src="{token url}" width="{square width}px" height="{square height}px" />
<!-- add more tokens or images here, like spell effects -->
</p>

So if your DM posts a map, you could use it and overlay your token.   Once the map is sized, I just experimented with the left, top position to align the token to a grid and resizing the token to visually match the grid.  If it was a perfectly trimmed map, you could count the squares and calculate a cubes pixel dimensions.  In my experience, maps aren't trimmed so trial and error works best. 

I will say once you've placed your token in a square, you should certainly try to use math for movement.  In the map above, the tokens are 28px so moving 1 square up and 2 left effectively be top - 28, left -56.

Of course, I had the feeling the page render differently in the post vs. preview.  They are scrubbing the style from the text in the post but not the preview.  So frustrating!