I'd tend to use a set range of sprites, say your lives variable is called LIVES, and you have a little 16x16 heart image loaded as image 100
For n=1 to 10
if n<lives
sprite n+50,100,n*16,0
else
if sprite exist(n+50)
delete sprite n+50
endif
endif
next n
That would step through 9 sprites from 51 to 60, and create or delete them depending on how many lives you have left. I'd do this in a function that I call every time the game starts or a life is lost. I'd use a similar system for score as well, like having the digits as images then convert the score to text and check each element, creating the sprites as I go.