You never know when you're going to need some grass. I'm always on the hunt for stock of the most mundane things and never able to find them.
Then there's the task of finding stock where the artist doesn't demand an arm and a leg for the use of it.
That said, here's my list of common sense rules: (you'd think they were common sense)
RULES FOR USE OF MY STOCK
If you use any of my stock, you must credit me in your artist's description and notify me of each stock use.
MAKE AN EFFORT. Changing the colour, dropping a filter or texture over, conversions to black and white or adding a frame is NOT A MANIPULATION. Do not submit derivative works to the photography gallery. Violators of this rule will be reported.
Please, respect my models. Do not make sexual remarks or lewd comments. You will be reported for this behaviour. (I don't have any idea how you can make a photo of grass lewd...) *eyes Rog*
No one is permitted to use my stock in deviations that promote hatred towards animals, people, religious groups, races, or any other act prohibited by dA policy. Use of my stock in pornography or fetish images are also unacceptable. You ARE allowed to use this stock in religious/spiritual devotional work so long as it does not condemn other religions. This stock provider does not care who you pray to.
dA Prints are ALLOWED. Feel free to submit your work as a print, provided you have followed the above regulations. Please notify me so that I may add it to my wishlist. OTHER commercial products NOT provided by deviantART require my written permission. (And I'm generally a push-over)
You may post derivative works containing my stock offsite in personal websites, portfolios, forums or what have you PROVIDED you credit me as you would submitting your work here.
Have fun already!