How to change the size of item-avatar in ionic?

I am developing an app using ionic framework. I have used item-avatar to display an image.

How do I change(increase) the size of the image displayed in the item-avatar? I was suggested the following CSS:

.list .item-avatar{
width: 20px !important;
height : 60px !important;}

This increases the content size(size allocated to the div tag) of the item-avatar as a whole but the image size remains the same. Is there any way to increase the size of the image displayed inside the item-avatar?