We can sort this problem out for you.
You can create a parent list that contains all 12 images from the A+B lists.
Let's call this parent list ImageList ...
1 Image 1A
2 Image 2A
3 Image 3A
4 Image 4A
5 Image 5A
6 Image 6A
7 Image 1B
8 Image 2B
9 Image 3B
10 Image 4B
11 Image 5B
12 Image 6B
Create one contructed list that selects from the A images and one constructed list that selects from the B images and then combine the 2 constructed lists. The parent list for all of these 3 constructed lists will be ImageList.
You can now have access to the 6 randomly selected images (1 from A and 5 from B) via teh constructed list ABSelConList.
Use the following ...
1st image - [%ListLabel(ABSelConList,1)%]
2nd image - [%ListLabel(ABSelConList,2)%]
3rd image - [%ListLabel(ABSelConList,3)%]
4th image - [%ListLabel(ABSelConList,4)%]
5th image - [%ListLabel(ABSelConList,5)%]
6th image - [%ListLabel(ABSelConList,6)%]