I don't want to put on extra work for you, but I'm still gonna tell you how to make more than 8 frames work in Step'n.
OK. So I opened up Nyami_Idle.sprite.
[Sprite]
Texture=Nyami_Idle 4x2.png
Frame0000=0
Delay0000=.25
Frame0001=1
Delay0001=.1
Frame0002=2
Delay0002=.1
Frame0003=3
Delay0003=.1
Frame0004=4
Delay0004=.1
Frame0005=5
Delay0005=.1
Frame0006=6
Delay0006=.1
Frame0007=5
Delay0007=.1
Frame0008=4
Delay0008=.1
Now all you have to do is make another frame. How many you want. So like add Frame0009=.
Now the number next to it tells which sprite it uses. See that Frame0005 and 0007 use the same thing, that's because they use the same sprite. ALWAYS make an extra space/sprite at the end that you won't use. It doesn't work, and if you use it, the game will crash.
Now the Delay000X= is how many seconds that frame stays. I normally don't mess with this seeing as .1 is good enough.
The Texture= at the top is the name of your file. The 4x2 should be self explanatory. | 
(Still may be lazy to go over if want to do character...)
