Hi Christian,
Images that are embedded in knowledge docs are stored in an attachment repository - so technically, regardless of whether you upload an image, or select one that is already in the repository, it works the same way. Now, as for the reason why you cannot see the image after saving the changes, this could be due to a misconfiguration in the repository, OR could be a bug. There were several bugs for this that were fixed by the cumulative patches for 14.1. The current cumulative patch level is CP3 - which is 14.1.03. I would recommend that you have CP3 installed, and if so, and you are still having the problem, then it would be best to open a support case with CA Support and we can troubleshoot the issue and assist you on it. If you dont have the CP3 patch installed, I would recommend getting that put in place first, and then reach back out to us if the problem still occurs.
As always, it is VERY important that you first test any patch or fix on an appropriate test system prior to installing it in a production system.
Thanks,
Jon I.