I'm new to Moon+Reader Pro, but based on what i can see, in visual settings you have your choice... you can select a flat color (and I agree their interface for this is HORRIBLE), or a background image.
If I go to background image, there's an option at the bottom that allows me to download one of my choosing... there's a decent selection. Also, you can bing search for 'android background' and choose 'images', and you should find a slew of em.
I think this is what you're looking for, though... definitely not lilac... maybe more of an antique blue? I just ripped the color from the link you gave and created a plain old background in photoshop in color c5e7ce. Another one in same color w very subtle watercolor wash to break up the 'sameness'.
Hope they help! Should be large enough to be a background for pretty much any device. Not sure if it'll allow downloading of images I post here, so there's dropbox links, as well.
Plain background
https://www.dropbox.com/s/9jf3ex1nds...round.jpg?dl=0
Watercolor background
https://www.dropbox.com/s/r0v65phltf...color.jpg?dl=0
Forum seems to only post fullsize images, so here's where you can view them...
http://s807.photobucket.com/user/ora...?sort=3&page=1
rachel