You can try out Darkroom Booth or use an unlicensed copy
to design templates.
On the Downloads
page, click the link for the latest build to download and install Booth. When you launch the
software, skip the activation and the software will go into trial mode.
In trial mode, Booth is not time limited but does watermark any prints
or email output with our logo and video recording is disabled. You can
create, edit and layout screen and print templates with the trial for
use on an activated version and the watermark will be removed. Here is a link with more info regarding using an unlicensed version to design templates