You look at their parents in person and can always hope the breeder might share with you pictures of or in-person the grandparents of the pup you are interested in. Make sure they're real and not just "posers"

. And perhaps even take a look at the offsprings of the past litters of the same pairing, and so forth. Looking at the many puppy pictures in YT members' photo albums and also those posted in the general pictures forum of YT, helps to see the transition between a certain kind of "puppy look" to its adult appearance. Sort of the "before" and "after" pictures. Find an adult or several on YT you love the look of, see if pictures of their youth has been shared and/or their parents as well. Otherwise, skip all that and just politely ask if they wouldn't mind sharing with you the name of the breeder they used for their dog and also, if they would be so kind as to share with you also, the name of the sire and dam. That way, you might have a chance at getting one who looks just like theirs and a full blooded sibling at that!
Good luck on your search!