Aha, I was slightly wrong earlier. It IS using your images, it’s not getting to that Credly point. However, it’s using the custom image size named “badgeos-achievement” which is getting registered at 100px by 100px.
It also appears that there’s no filter at any point along this path that you could change which registered image size it calls. I can’t call this a bug, but I can call this a lack of customization. The closest you’ll find at the moment is this filter “badgeos_render_achievement” and it’s going to have all of the html that goes along with each badge. That one would, at best, require regex to fetch the image url to change.
That said, I’m going to file a GitHub issue for you for some filters for changing this. I agree that there should be a way to use a different image size, instead of having 100×100 forced on you. If we get it in soon enough, it could get in the next release. Stay tuned.