Alexander has sent pictures to a total of 1 original gallery + 5 new galleries = <<1+5=6>>6 galleries.
For signatures, he has used a total of 6 galleries * 2 pencils per gallery = <<6*2=12>>12 pencils.
So of the pencils that he used, 88 total pencils – 12 signature pencils = <<88-12=76>>76 pencils for drawings.
At the first gallery, he used 9 pictures * 4 pencils per picture = <<9*4=36>>36 pencils.
So in the new galleries, he used 76 total pencils for drawings – 36 pencils at the first gallery = <<76-36=40>>40 pencils.
The new galleries received a total of 40 pencils / 4 pencils per picture = <<40/4=10>>10 pictures.
As the new galleries all receive equal amounts of pictures, each gallery must have 10 pictures / 5 galleries = <<10/5=2>>2 pictures per gallery.
#### 2