I decided to create a guide to the Sandbox, a part of the forum that definitely needs more love.
What is the Sandbox?
The Sandbox is a place where you post your "in progress" pieces. If you're insecure about your wall/indy art or you're just facing an artist's block and in desperate need of ideas, this is the place to get some feedback that will help you to improve and get your artwork done!
Additionally, if your submission has been deleted because of quality, you can post it here. Members will give you tips on how to improve your work in order to make it back into the gallery.
How do I upload stuff here?
First, keep in mind that even though not explicitly stated, all rules outlined in the MT Policy apply, so please make yourself familiar with them. Next, you need to upload your image to an image hosting site. ImageShack, Photobucket, and tinypic are good places. After you upload your image, there should be some code you can copy. Copy the one that has "BBCode" or "forum code". Use the one that says "thumbnail mode" if it's there (this will post a thumbnail, and when you click it, goes to the full image).
Go to the Sandbox, and click on "New Thread". Give it an appropriate title, and paste your image code that you copied earlier into the body of the thread. Also, write some information about what you did, and what you need help with. It also may be helpful to link to any scans you've used. Please do not post more than 3 pieces at a time, as it is much easier to give constructive feedback on a smaller number of items.
Note that you MUST include links to the resources you used, especially stock images, such as background and main image
This is the most important part. The Sandbox depends on people's comments in order to function smoothly. If you say "I don't know, it looks good to me", you aren't really helping. Members post work here in order to get tips on how to make their pieces look better.
But, remember to be polite. Saying things like "this looks like crap" is not constructive criticism. By participating in the Sandbox, you are expected to help by posting things that could be improved (like extraction, composition, resources, quality, etc.)