I guess the GLSL shaders are disabled by default in the official mame build, maybe that's why it's not working. I'll try to compile it myself and try again, then I'll post the result here.
Also, I would like to make a suggestion to the Pictures area/tabs: the tabs row can get crowded very easily with all those tabs enabled, and you end up with a very little arrow control to scroll through the tabs, which is cool but not that good. Some tabs will always be offscreen. My suggestion here would be to have an IMAGES tab, where you would have some sort of table containing all images for the selected game/system. And when you click on one of them, it would pop up a new, larger window to display the selected image, and this new screen would have two arrows, one at each side of the image, so you can navigate through all the images in this new window. Then, when you get tired of viewing such images, you close the window and it would return to the main screen. This would benefit the tabs row a lot and you would have an image tab displaying all available artworks at the same time. And if an user is too lazy to keep scrolling through the images tabs/window, he will have all available artworks right there in one screen.