I think a key issue is knowing whether or not its ok to use someone elses idea.

What is an idea:

i‧de‧a  /aɪˈdiə, aɪˈdiə/
–noun
1. any conception existing in the mind as a result of mental understanding, awareness, or activity.
2. a thought, conception, or notion: That is an excellent idea.
3. an impression: He gave me a general idea of how he plans to run the department.
4. an opinion, view, or belief: His ideas on raising children are certainly strange.
5. a plan of action; an intention: the idea of becoming an engineer.
6. a groundless supposition; fantasy.
7. Philosophy.

a. a concept developed by the mind.
b. a conception of what is desirable or ought to be; ideal.
c. (initial capital letter) Platonism. Also called form. an archetype or pattern of which the individual objects in any natural class are imperfect copies and from which they derive their being.
d. Kantianism. idea of pure reason.

8. Music. a theme, phrase, or figure.
9. Obsolete.
a. a likeness.
b. a mental image.

In a more simplified way of explaining for artistic work: An idea is simply somebody's interpretation of a topic, a thought, a representation.

Basically this means that one persons idea [for instance a word can be the "idea"] can be represented very differently to another persons idea of the same topic.

All too often it is mentioned that another deviant has stolen someones "idea". However I would like to stress that using someone elses idea is a great thing. It helps you to build your gallery, and to create more work unique to yourself.
I'm not saying make a replica of someone elses work. But use their idea, and create your own masterpiece.

It is not against the rules to use other peoples ideas. And idea can never be copyrighted to an individual. If I was to ask you to create your own interpretation of the word "Hassle-free", I can almost garentee that you'd have different drawings/photos/stories/whatever, submitted for that.

While ideas cannot be copyrighted, images can be. So in saying that, please do not mistake me for saying its acceptable to copy someones work without permission. I always ask someone if i feel like i'd like to digipaint their photograph, for instance. Its just etiquette.

If you do not have ideas for your art, go through the Stockart Gallery, which contains literally hundreds of photos that you can do anything you like with.
-Make a story about a photo you find there.
-Recreate the photo with digital airbrushing/etc
-print it out and paint it with your favourite medium.

there are so many options out there! Take advantage of deviant art's resources and the many helpful deviants here, and have fun!

so remember:

Ideas are unique representations by individuals and CANNOT be stolen, but merely reinterpreted in a different way!

thanks for reading!