Image ad sizes should be correct to present the beste experience for the customer. It’s a god habit to create all the ads at once in Photoshop and then publish them to the different ad providers.
Image ad size for Twitter is 800 x 320
Twitter uses a image that is 800 pixels wide and 320 pixels high for the website card.

Image ad size for Facebook is 1.200 x 628
Facebook uses a image that is 1.200 pixels wide and 628 pixels high in general.
Read more on this Facebook page about ad dimensjons
Facebook’s 20-Percent Text Rule on Ad Images
Ads that have more than 20% of text in their image won’t be approved to run on Facebook or Instagram. Too much text can look like spam and make people think that your ad is low quality. Make sure to use the headline and body of your ad to tell people more about why you’re advertising and what you want them to do. Read more about the 20% text Facebook rule here.
You should use the Facebook grid tools to check if your image is allowed by this policy.

Image ad sizes for AdWords is 20 different image ad sizes, plus, plus
Adwords requires at least twenty different images when you want to utilize all the available ad spaces. AdWords image ad sizes is a true maze. There is 20 standard dimensjons and in addition to this there is different regional sizes. An overview is available here. In addition to this the wizard that generates HTML5 ads and other specialized ads requires other image sizes. In addition to the this the requirements tend to change periodically.
We thin it’s helpful creating a set of layered Adobe Photoshop files that we use as templates. This is the list of sizes uses when creating Adwords ads by default:
