I'm sure this may seem like a sophomoric question to some, but after reading many of the message threads in several of the forums, I am concerned about how I go about creating the images I post on this site. As I state in my bio, I'm not a graphics professional (my girlfriend is, and is always willing to answer questions, but not about 3d topics), and therefore anything I post has been done as a "hobby", strictly non-commercial and just for fun. I have not bought any add ons as yet, and just download free textures, materials, and models as available on sites like 3D cafe, etc. But, if I make changes to someone elses model, am I going to attract their wrath? I will not take credit for an image or model that I haven't created, and I do try to identify the creator or download source. I've read some rather heated exchanges about some of the artists finding someone's work on another site, without their permission, and about "ownership" of purchased add ons being debated if they are on another computer, etc. This is confusing to me, and I don't want a very fun, interesting and growing hobby to suddenly land me in a world of trouble. I understand that there is an eclectic mix of individuals posting graphic work here- some like me, others established artists. My blissful ignorance could land me in trouble. I look forward to comments on this that could enlighten me as to whether or not I am taking necessary steps before posting things. Thanks in advance.

You're allowed to alter things for your own personal use. If you're not selling images and not redistributing the things you've changed, you're fine. If you sell your images, you should make sure that the freebies you've used allow commercial use. Some will say yes in the readme; some others may not say so, but the creator will give permission if you ask.