never bought so no need to worry about refunding. just thoughts that come to mind. I believe it is the personal moral right for people to be able to make money with ideas and media they consumed in childhood so again i dont have any personal complaints there, but if you feel the content is not usable in a copyright commercial product as is it may be worth a warning. In general, when dealing with style issues you should try clean room approach and neglect a key reference, though you are right that can be a hard nut to crack and many do use references and it works out, you have several working tilesets for example, i just dont think these sprites pass the same way.
Viewing post in GBC NPC Overworld + Highlight + Free Version comments
up to you what you want to do. Personally I think even something that isn't usable as is is useful if it can be modified freely to get the rest of the way there. There are a lot of off the shelf sprites and stuff I see everywhere that I plan to use as components more than anything else. otoh if you want to make the sheet again as a challenge as long as thats worth your time.