Hi LouisGac,
I've replaced the logo.png with my own but I still see the original one. Then I've replaced also the Limesurvey_logo.png in the same folder: same result. Then I've changed the resolution and size to the same values as the original one, but even after a reboot of the sytem: same result.
Do you know what I'm doing wrong?
I use LimeSurvey-Version 3.14.8+180829
Thank you in advance! EDIT: I've found the mistake: You have to replace the logo.png in /themes/admin/Sea_Green/images/ instead of /styles/Sea_Green/images/. Now it works.