Unfortunately, campaign ribbons (awarded when a campaign is finished) are limited in size to 50 pixels wide by 20 pixels high. Campaigns can have banners which users can link to in their signature but those have a limit of 468 pixels wide by 90 pixels high.

We have several threads to help you with campaigns:

TUTORIAL: Armorama Campaigns

TUTORIAL: For Campaign Leaders

Campaign Ribbons and Banners

As for a starting date, you can always look at the picture in the first message in the Schedule thread to see when campaigns are starting/ending.

Campaign Schedule