Hi Varad,
Thank you for your interest in JPF and for reporting issues on the wiki. I just checked it now, and it seems that links are working well and that images are displayed. I haven't checked all the images but checked a few; if there is a particular one that you were having a problem with, please let us know. You could also try to access the page from a different machine and see if that fixes the problem. This information should be public, so you should have access to it.
I am not sure about the current status of the support of Java 11 and Java 12. You'll probably get other replies with more directions, but looking at #274 seems like a good place to start, particularly looking at the most recent comments and updates, and running tests. Looking at failing ones can give you an idea of where the limitations are, and possible solutions to it.
Soha