How can I resize and round the edges of a banner in the Dawn theme?

[Katsura]

Hello. I’m trying to change banner on my shopify dawn theme, standard banner image is fully stretched from left to right, I’m trying to make it smaller and round the edges, I’m okay with top banner being stretched but want to make other image banners smaller with rounded edges if It’s possible, attaching an example photo of how I want it to look, will really appreciate If anybody can help

My shop: www.parsek1.com
Banner example: https://kakimori.com/

[Ujjaval]

@Katsura
You want image something like this ?

[Katsura]

More like this, so products align under the banner perfectly and banner is centered as well