Path overlay help

[Hypno KK]

I know you can lay path patterns over the default ones if they have at least one transparent pixel, but where do you find those? I've searched and found only a few. Are there any sites/resources/designers you'd recommend for this kind of thing?

I'm especially looking for dark wood and dirt paths that I can use like this, so if you've got any recommendations for that specific thing, please let me know!