In your last screenshot, the three tiles on the right appear to have a semi-transparent style applied to them. Did you want them to look different and if so, how?
Media Tiles can use Styles just like any other tile, so you can use semi-transparent or opaque (solid) colors as a background if desired. You can always edit the Style applied to the tile and use a Custom Style (or even custom CSS applied to a named style) if desired.