This is very simple thing that if you are saying 100 words and another person showing you a single image, and both persons wants to say on same topic. what you do you think, which will be better? of course images gives you best impression. Now a days there are many examples in internet world. There are lost of website for buy and sell, classified, news, Facebook, etc they allow user to upload image just because of better understanding.
What you need to do, first you have to install a plugin comment images and activate it. No need to do any setting and configuration for this plugin. to verify go to your blog . website page scroll down and see the upload image option be there.
The classified website or online stores are real example, that what they are selling they showing via image that what they are selling. Suppose if somebody is selling car through classified website without image, you can understand that how many questions raised in customers mind. instead of this if the seller upload images with some text material, it will be more clear and no question will be raised, just they will make deal. So this is the importance of allow uploading images in comment. You can do it easily as I have mentioned above.