limiting image size

Hi,

I'm helping to write a new user manual for Tor Browser [1] in Mallard.
It's a great, simple documentation format, and we're happy to be using it.

One of the problems I've encountered is that linking to detailed .png
files with the "<media img=" tag is that they show up (when the Mallard
source is viewed in yelp) at a very large size. Is there anything I can
include in the tag that will constrain these images to smaller dimensions?

Thanks for your help.

[1]: https://www.torproject.org