This will work.....
For n = 1 to 100
Number$=Str$(n)
Title$ = "Tileset0" + number$ + ".jpg"
Load Image Title$,n
Next n
Edit: Actually that will not work, not enough zeros. Hold on....
For n = 1 to 100
if n = 100 then zeros$ = "0"
if n < 100 then zeros$ = "00"
if n < 10 then Zeros$ = "000"
Number$=Str$(n)
Title$ = "Tileset" + Zeros$ + number$ + ".jpg"
Load Image Title$,n
Next n
If you make something like this, test it like this...........
Set text opaque
For n = 1 to 100
if n = 100 then zeros$ = "0"
if n < 100 then zeros$ = "00"
if n < 10 then Zeros$ = "000"
Number$=Str$(n)
Title$ = "Tileset" + Zeros$ + number$ + ".jpg"
text 0,0,title$
wait 500
Next n