For those who are going to submit images for Community Promotion Ads, I figured that I would share some info to make things easier for you. I am basing everything off the original image added by Grace Note:
The colors used here are primarily (all RGB):
Dark Blue: 45,77,98
Mid Blue: 53,171,221
Light Blue: 172,218,218
Light Red: 238,231,223
Background: 243,243,243 or 250,250,250
As stated, the dimensions should be 220 x 250. The sample ad has a border around it, you can use this basic one as a template for future images if you'd like:
Note: The real background color for the site seems to be 243/243/243, but the image used by Grace Note and the template above uses 250/250/250. It probably isn't visible to anyone by eye, but hey, just throwin' it out there
The font size used in the image is (most likely) 12pt. At that size the text is easily readable (as seen in the logo), so use this as a starting-point when deciding how big to make text.
The font used for the Workplace Logo is Cosica MX Regular Condensed which is not free. If anyone knows of a good alternative, please share it here.
I have not found a better quality logo to use than the one used in the image. So I just recreated it since it's pretty simple, and made it really big so no matter what size you reduce it to, it should look decent even if you change the background color of the ad, etc.
Note: The logo is copyright of StackExchange and should not be used for nefarious purposes that contradict their terms of service, particularly 2. Network Content which says, "All trademarks, service marks, and trade names are proprietary to Stack Exchange and/or third parties. Subscriber shall abide by all copyright notices, information, and restrictions contained in any Content accessed through the Services.", which applies to logos which are stated in the footer of each page as: "site design / logo © 2014 stack exchange inc"
The original site design post has many images. You can also take screenshots if you want to use the stapler, the robot, the coffee machine, etc.