It may not have the Visualboy 'Filters' on, but the renderer being used is still blurring it out, thus creating what resembles a filter.
THIS is what a non-filtered, non-blurry GBA picture is supposed to look like:
Maybe, as I said, you're resizing them in the emulator or in the web browser or something?
This is the same picture, resized:
If it's difficult to see the pixel squares, it's filtered. Maybe it's the renderer filtering it (switch from DirectDraw to something else, I know DirectDraw often blurs out the shots but it varies upon your graphics adapter), maybe it's a filter you aren't aware it's on, but it's definitely in your pics.