I appreciate the effort, but alas the picture in mind is none of the above.
I also didn't expect so many pictures that matched my initial description, so I'll narrow it down from what I remember:
The image is likely a sketch (or otherwise monochromatic light blue-white) of a lass wearing a puffy-sleeved dress, facing rightwards, likely resting her head on one of her left hands, reading a book.
I believe I came across the picture in a multi-limb thread on /d/ back in 2014.
I've now also scoured Danbooru and Gelbooru to no avail: The upside to all this is I now have a lot more multi-arm stuff in general.