It looks like there are several css elements out of whack. The sign in page doesn't even appear to be responsive. Have you made any changes, besides adding the background image?
One consideration instead of setting the sign in wrap to transparent is to use an rgba color. If you set it to transparent, you won't be able to see the dark text with the background "i.e. rgba(255,255,255,0.6); creates a white background with an opacity setting so you can see what is behind it.