If text readability is a problem for you, I think you may simply want to cut out the page background from the left side and just leave the girl. I didn't use that edit because the page's color was darker than the regular quest
page color for some reason and quests being listed in yellow font would tend to blend into the page's yellow color. (The background of the left side was meant to be black, after all.) Alternatively, you may want to reduce the opacity of the girl if text that goes over her comes out unreadable. You could also do this to the page, but NOT the whole window. A questlog edit of my own creation comes out like this, for example:
On the left, I leave the background black and make the image less opaque to make yellow text more readable. On the right, the girl I put under the quest text is somewhat transparent
so that text is more readable.
Of course, you'll still want to avoid colors that may cause text color to blend into the background, like any large blocks of dark colors or yellows.
It doesn't look too bad from your screenshot, but I'd probably end up not finishing any quests and just stare.