if you are familiar with classes and even if not, this would be a perfect opportunity to learn.

turn your pictureboxes into objects with falling speed, position, and picture properties with a contructor

just something simple like

class box
private FSpeed as single
private PosX as long
private PosY as Long


public sub New()
'for speed use 3+ a random number between 0 and 5 say
posy = top of course
posX = random numberbetween Left and width
end sub

create some functions to get the fspeed, posx,y inside the class

then you can create a list of boxes

public boxes as new list(of box)

then with every tick event if theres less then 10 in the list add a new one

boxes.add and it will calculate everything for you

then just handle the movement using the functions in the class