Here's my view of things. With high sizes of random girls packs, one of two things is going to happen. One, if the game loads all the girls' pictures at the beginning of the game as I believe it does, having a good number of huge random girl packs is going to slow things down at the start.
If the game loads the pictures as needed as DarkTL suggests, having huge random girl packs is going to make the game slow down as you start to have large total numbers of girls. I do know that the game loads in pictures for every instance of a certain girl. Five instances of the same girl with a 10MB picture pack is going to have the game load that 10MB five times, for a total of 50MB loaded into memory. What happens when you have 100 girls, each with 10MB picture packs? The game takes up 1GB of system memory.
In either case, having large picture packs for the random girls isn't a good idea. It's forgiveable for the unique girls, since you only get one of each of them. But for the random girls which should be making up the majority of your brothel girls, it's a poor idea for each of them to be taking up a lot of system memory.
I don't want to argue over this too much, so I'll just say that as long as you're hosting your own random girls packs, you're free to make them as large as you feel is prudent. But in the interest of keeping the game run smoothly, and also in the interest of keeping my download size as low as possible, the random girl packs that will be included with the game will have ONLY one picture in each category.