As you know we have 1k+ blocks and constantly evolving so it will not be easy to give dimensions for each static block, although it can be easily got from Image upload area as shown in the sample image. Size is displayed for each image.

Here are some of the key sizes for the dynamic blocks..

Course Card /Course Thumbnail:

1: Course Card Recommended Size: 350 x 197

Home Page Blocks:

2: Home Page Banner Background image: Recommended size : 1192 x 404

Course Sales Page Blocks:

3: Course Sales Page Banner Background image: Recommended size : 1192 x 720

4: Instructor(Your) Bio block Background Image: Recommended size : 1192 x 298

5: Pricing Block background: Recommended size : 1192 x 742
6: Testimonial People photos on testimonial block: Recommended size : 120 x 120

Other
7: Your profile image in Account > Profile : Recommended Size 200 x 200

8:  Logo recommended dimensions: 250 X 100