Action Details
Requirements and how-to articles for Twitter's action:

paid action
Multi-image tweets appear in users' feeds and can have up to four images.

You need this to get it done:

File format: .jpg/.png (.bmp/.tiff not supported)
Maximum file size: 3MB
Minimum image resolution: 600 x 335 pixels
Aspect ratio (two images): 7:8
Aspect ratio (three images): One 7:8 on the left, two 4:7 on the right.
Aspect ratio (four images): 2:1
Tweet Text
Text to accompany the images (maximum of 280 characters.)
The URL you would like to send your audience to.
Requirements missing or found errors? Report

How-To Articles
A list of useful links for you:

Twitter Business - Advertiser creative specifications
Official information on creative specs for ads.
Link missing here or found errors? Improve How-Tos