Can I give Automator apps a window? Can I create a window / UI for applications created using Automator?
Or is this just not possible with Automator apps?

Background:
I created an "application" through Automator, and dragged the app into the Dock and it works fine. However the app does not act like an normal app. e.g. I can't seem to "open" a window for it, or have it in the CMD + Tab menu. 

Note: this is a follow up question to: “drag n drop” application to convert images to base64 string for web development

SOLUTION

As per answer below I used the free platypus. I simply created a new script through the UI and copy and pasted the code I'd used for my Automator app:

for f in "$@"
do
    openssl base64 -in "$f" | pbcopy
done


Note: this copies the base64 string to clipboard, and thus I assume its only good for simple imgs (which is all I want it for)
Create the application with Platypus instead:



The application window looks like this: