@Volker_E, what might be helpful is to define a canvas size for all of the logos to fit in (eg. 50 px high, 120 px wide) and to downscale all of the logos to fit and be centered within this field. The main problem with this solution is that tall, thin logos may become harder to read, but it helps to create a more unified look and to make spacing between elements more cohesive.

This open task is tagged with Wiki-Loves-Monuments 2018 which was two years ago. If this task was/is resolved, then please update the task status. If this task was not resolved but is still valid, then please update the project tags to include at least one active project tag, so this task could be found when looking at that other project. (Without reaction, this task might get declined at some point.) Thanks a lot!

Removing Wiki-Loves-Monuments 2018 tag as that was two years ago; adding general Wiki-Loves-Monuments tag.