Raise Of Sculk mod copyright worries

Almost certainly not. It's still generally bad form to take someone else's work; but as long as you're not selling anything you're probably fine. If you've significantly edited stuff, (remixed sound effects, changed textures or used them for templates, etc.), that's a bit better. Regardless, still a good idea to credit anyone who contributed to the final project, or ask the original creators if you're worried about it.

If you don't know the license of the files, it is not allowed in our terms of use to use such textures.

Only use them if they are licensed under a license that allows the use of them.

You will not get sued, but your mod will be taken down and if repeated action is made, account could be suspended.