Can anyone confirm if using a number of new portraits that differ in number from vanilla causes any problems or not?

For example, in vanilla the Barbarian culture has 151 portrait images from which to draw; what if I only had time to create (say) 40 new portraits (replacing the 151 vanilla) for a mod. I know they could be duplicated but even that takes time...just wondered of anyone could confirm anything either way...do the random sequences call upon a range based on the number of portraits or upon a hard-coded value? If the latter then does this have an undesirable effect in game?