It's so f*cking annoying!
Every time at the launcher start, the game will download the default-picture file from their server and you have this sh*tty loading screen again. If you make a right click on the Ffile or the folder to activate "Read Only", it doesn't work, cause the launcher will try to overwrite the file in an endless loop.
Your technic worked (once), but only as long as you've play the game, after closing and launcher-reboot, the f*cking launcher overwrite the picture-file again. *ARGH* Go to hell, Bioware!