Have you considered using a "standard" Free licence, e.g., Creative Commons BY ( http://creativecommo...icenses/by/3.0/
) or any of the other Creative Commons ones?
(Whilst your terms may seem plain and simple, copyright can get surprisingly complex in grey areas - using a standard licence makes it much easier for games using it to be distributed through various systems, e.g., Linux repositories; or there are questions such as derivative works.)
1, 3, 5 would be covered by Creative Commons BY. Rule 4 is probably the difficult one - can I ask why this is important to you? It would mean the graphics couldn't be put on a place such as opengameart.org , meaning less awareness for your work. It would mean the graphics are lost to the public if say in 5-10 years' time your webhost is down. Note that if someone did post the graphics, they would still have to credit you and link back to your site. Rule 2 you could probably get anyway just by asking.
(Apologies for nitpicking - but it's a shame for someone to put so much work into good graphics like this, and for someone to have a game to use them, but they don't get used because of licensing issues.)
Edited by mdwh, 01 June 2012 - 07:45 AM.
Thanks, it's always good to see people sharing work for others.