Can I use existing theme html to develop a new theme? Example inside

[thecybertech]

Hi, I'm very new and this is my first post. I tried to look around for more info on this before posting but could not find any. Anyways read if you would and tell me how I did for my first basic wallpaper type theme. I used paint shop pro (havent quite got used to photoshop yet) and made the finished images myself using royalty-free images.
I used Suriks changing background theme and replaced the pictures with my own and edited the html to make it work. This is for the main in phone changing/fading in and out pictures but the lockscreen I made myself. Is it OK to do something like that and upload into the store for free or sale?

[sgt.pepper]

i don thtink so. i would ask him personally.