For more information on using your Etsy Mini:
Part 1 - What is an Etsy Mini? How to build an Etsy Mini
Part 2 - How to post an Etsy Mini on your blog
Part 3 - How to post an Etsy Mini on your Facebook Page
It is possible to make an Etsy mini from another store, for example if you wanted to have an “artist of the week” Etsy mini on your blog. The trick is to make an Etsy mini for your own store, in the dimensions and size that you want your featured artist to have on your blog. Then you need to find their user_id and replace yours for theirs.
Here's an example. Let´s say I wanted to make an Etsy mini from this great store I found recently called reclaim2fame.etsy.com. First I would build an Etsy Mini for my own store, making it the size and dimensions I want to show reclaim2fame´s listings in.
This is the code I get for that:

Now, I want to turn it into an Etsy mini for reclaim2fame´s store. All I need to do it look at his Etsy shop Policies page. The url will look something like http://www.etsy.com/shop_...user_id=5932649. The bit I need is his user id 5932649.
So I take the Etsy mini code for my store, and I replace my own Etsy id with his like this:

By using this technique you can create an Etsy mini for any store you like, without needing to convo the seller to ask them to build one for you.
For more information on using your Etsy Mini:
Part 1 - What is an Etsy Mini? How to build an Etsy Mini
Part 2 - How to post an Etsy Mini on your blog
Part 3 - How to post an Etsy Mini on your Facebook Page