What's the difference between a template and a background?
A new template gives your blog a completely new look by changing everything, including font styles & colours, number of columns and their widths, and usually includes separate header & footer images.
A new background only changes the background image of the template you're currently using.
Why do I need to use the Minima template to use your backgrounds?
The main reason is that I have sized Blog Splots backgrounds to suit the Minima template.
You may find they look fine with other templates, but on the other hand, you may also get some funny results.