Hi Alex,
The images showing up at the wrong size is a plain css issue. The gallery is marked up as a list item, which contains a link (<a href...), inside which sits the image which is 155px X155px ,as you have intended. You can check this by inspecting in Chrome's developer console or Firefox's firebug. Now, this nice little list item has got a fixed dimension of 150px X 35px. Beyond that, it doesn't like showing the image.
Now these preliminary checks, are something we would like you, to do first, before raising a ticket.
Kindly understand that this is an open source plugin and we are really hard pressed with the resources and time to solve issues that aren't related to the plugin.
So, as is the case with most open source projects, we like a little patience and/or a few pre-checks before we can solve issues. Kindly give us the time, considering the time zone difference, to get back to you in any case.
Finally, do keep reporting any further issues. We might take a little time, at times, but we'll definitely get back to you. In case you'd need priority support on any site of yours, please consider contacting us commercially.
Regards.