From: Maryssa Skytower
1. Can I take a color swatch from a RL furniture maker and create a texture from it without getting into trouble?
Good question. All images are copyrighted at the time of their creation, including the kind of swatches you're talking about. Unless the owner of an image specifically grants you permission to use it, it's off limits.
That said, it's pretty unlikely anyone would ever be able to tell that a texture was sourced from any particular swatch, since swatches are so common, but that's not really the point. Doing the wrong thing just because you think you're likely to get away with it doesn't make it the right thing, as I'm sure you know.
In any case, it's not like doing the right thing is all that hard. There are lots of easy ways to replicate materials. It's just a question of learning the software you have. Often if you just Google for "Photoshop ______ tutorial", with the blank being whatever it is you're looking to make, you'll find tons of walk-through's. If you're not using Photoshop, you can adapt the instructions to your program of choice pretty painlessly in most cases.
And of course, you can also search for "GIMP ______ tutorial" or "PSP _____ tutorial" as well. It's just that there's so much more material written for Photoshop, that's usually the best place to start.
Beyond that, there are lots of other easy solutions.
If wood is what you're after, Wood Workshop from Spiral Graphics is a good place to start. It's free, and it does a nice job of creating wood base textures. The results will look contrived and fake, though, without a good degree of post processing in Photoshop or whatever your image editor of choice happens to be, but for a starting point, it's great.
For upholstery such as leather, canvas, etc., there are all kinds of techniques you can employ to create convincing materials from scratch, depending on what software you're using, or you can always take your own photos. Often just running over to Walmart and spending a couple dollars on a real swatch of fabric, which you can then scan (assuming you have a scanner, which you really should if you're doing any artwork at all), is a great way to go.
Also, iStockPhoto.com is a great source. Images only cost a couple dollars each, depending on size, and there are literally hundreds of thousands, if not millions, to choose from. I've used iStockPhoto pics as starting points for textures many times.
Finally, don't be afraid to invest in third party filters. There are some very good ones out there for creating all manner of materials. All will require post processing (shading, lighting, dirtying, etc.) in order to look realistic instead of contrived, but that's what being an artist is all about, of course.
From: Maryssa Skytower
2. I see a ton of gimp tutorials out there but are there any just focused on creating a new texture and not a clothing or hair texture?
Absolutely. Just do what I said above to search. You'll find tons.
From: Maryssa Skytower
3. Are there any inworld classes that could help me? I have found tons of tutorials on textures and building, but I learn better if someone can walk me through it.
I don't know of any off hand, but I'm sure there are plenty. Try searching in-world events for GIMP classes, or texturing classes, or whatever other keywords you can think of that might lead you to the right place.