I just use and upload to tiny pic http://tinypic.com/index.php , and add the image here like this Code: [IMG]URL IMAGE HERE[/IMG]
Select a rom on the main site first. Here is an example, ive selected a game that have no screenshots uploaded... https://www.romulation.org/roms/NDS/5531-Dragon-Ball-Kai-Ultimate-Butouden-(J).rar/ Under the screenshot box you can see an 'add one' button the rest is easy enough to understand even for a newbie...
Depends on how long the moderator takes to get around to it. Have to screen those by hand. I just cleared out the list though and I think it should be noted that we'd prefer gameplay screenshots as opposed to box art in the future. Cheers.
Depends on how soon you plan on starting, and whether the uploads fulfill the terms and condition as required of a proper contribution, as well as how soon an admin is available to evaluate your contribution which usually shouldn't take long. And yes, we don't want boxart images, username input screen images, and certainly not the game maker's logo screen nor the credit screen. The game's in-game screen is the better choice as will be most useful, although main menu screen is just as great.