I really hope that in the version of livery Designer there is an option to 'activate livery' for AI traffic as it is starting to get on my nerves. I don't know if it's to do with the difference in volume of traffic but I've never seen an AI ICE3M with my custom livery on it whilst in SEHS I see the unfinished one I started all the time. Sometimes it is on the second unit of a 8 car train even when I have selected the SEHS livery before I start a service.
And, conversely, custom liveries can appear where one doesn't want them, such as the Clinchfield SD40 on Sand Patch. A checkbox interface would be highly desirable.
It's one of those super basic conveniences that really ought to be a given, like sorting our routes by country, favourites, etc.