brahmnan

If you want user avatars to be displayed quickly and do not use external services, the module for generating “identicon” avatars using “canvas” is suitable for you. 
“Canvas” avatars will be generated for all users who do not have their own avatar images.

Identic canvas

This plugin creates user "identicon" avatars in "canvas" format using user email

sippsolutions

If you host your site in a poor environment, WordPress may fail uploading large images as the process of creating the different sizes and thumbnails takes a large amount of CPU usage.
With this Plugin the images are simply resized to a maximum dimension (of for example 1600 x 1600 pixels) right in your browser before uploading them. 
The nice side effect is that unnecessary big images are resized to a fine size to still provide a usable, qualitative image.
Logo credits: Picture graphic by Flaticon from Freepik.

Canvas Image Resize

Re-sizes images right inside the browser BEFORE uploading them.

Identic canvas vs Canvas Image Resize