Yes. As long as your entire message is under 5MB (either with one or multiple images), Twilio will resize your images to the necessary size for delivery based on carrier specifications. An API request with an image larger than 5MB will fail with an error.
If you prefer to resize your own images, we recommend that you follow OMA specification and send images of 500kB.
Twilio will only resize png, gif, and jpeg files. Other media files will not be resized.