Delsetray, it is much easier using a Family...
but without Family, I would create a global variable, and set it to a random number between 1 and 10 and then create a sprite for each possible result:
SpawnNumber = Round(Random(1,10))
Then
System Compare Variable -> SpawnNumber = 1 -> System Create Object -> Sprite1 on layer 0 at x , y
System Compare Variable -> SpawnNumber = 2 -> System Create Object -> Sprite2 on layer 0 at x , y
System Compare Variable -> SpawnNumber = 3 -> System Create Object -> Sprite3 on layer 0 at x , y
.
.
.
System Compare Variable -> SpawnNumber = 10 -> System Create Object -> Sprite10 on layer 0 at x , y
Note: you would want to have all those lines be sub-events of some code that decides when you need to spawn a sprite. If they were top level events they would continuously spawn sprites as long as the global variable has a value...