Hoi,
Your two forum posts from Kunena and jReviews explain the problem. Basically, JFBConnect will import the raw/full-size image into Kunena. Then, according to Kunena's own forum post (and what we know), the thumbnail images are only generated on-demand:
www.kunena.org/forum/159-K-17-Common-Que...?limitstart=0#124956
So, Kunena will automatically generate the thumbnails as requested by either Kunena or other extensions. However, the other extensions need to specifically tell it to generate the right size thumbnail for their needs. I don't believe jReviews is doing this request:
www.reviewsforjoomla.com/forum/index.php?action=profile;u=18
So basically, if you have Kunena set to create 200px avatars, but then tell jReviews to use 72px avatars, there's a disconnect since Kunena won't create that size unless it's instructed too.
You'll either need to switch your avatar size in Kunena to 72px or (as Alejandro mentioned) change jReviews to use the 200px avatars that are being created by Kunena.
There's nothing JFBConnect can do here. We simply hand off the avatar to Kunena to create thumbnails as it needs too.
Alex