Hi @lomyn.
On the bbPress install package, there should be a file called bbpress.css (under bbpress/templates/default/css). Just extract that file from the package, add the code at the end of the file, and copy it to your theme’s css directory.
The new WordPress 3.6.1 doesn’t have this option anymore. I know there are a few code hacks out there for changing the embed size, but those affect all the embeds on the site (including embeds on regular posts).
I was wondering: Is there a way to change the embed size for bbpress posts only?
