I thought that my cover explanation was easier, I was looking for a badass pose involving the main characters, but then I've found a deeper meaning!
"Annie's Solutions" is set in Britain at the end of the 1800s, so the style of the background and the chair is based on that.
The main characters, the uncle and the niece, are complementary and despite the differences, they share the role as main characters, supporting each other shoulder to shoulder.
Annie is younger and bolder than Scott, who is way more optimistic, her strong point is her knowledge and her smart deductions, that's the reason of the books in the background.
...yeah, but mostly is for the badass pose!