Add Alt text on Media Images while uploading - Umbraco

I am using Umbraco 7.5.3 and I want to add an alt text to media images while uploading or while selecting (On clicking submit) them using media picker. Is this possible?

I have added a property to Image Media Type. This way it is available for all the images I have in the CMS.

But another question I am getting stucked with. Is it good or bad to change inbuilt Umbraco data types?

Any help appreciated.

Thanks in advance!

Solution

For this, I have added an alternative text property to the media Image type. (Settings -> Media Types -> Image).

You can see the below image.