is there any chance to read out the "image title" informations of an random album thumbnail?

Yes, using the object model.

thanks, I can't figure it out. any hint/link?

I assume you are using the function printRandomImageAlbum(). In that case you have to use the "get" variant to create a custom function.

IF you are talking about the album thumb within the album loop all album class methods are documented on the functions documentation on the user guide.

In any case you need to read the object model tutorial and have some understanding of PHP: