If an icon is clickable (this is indicated by a thick brown border, making it slightly higher than the rest of the icons) it will lead to a footnote at the bottom of the page which describes any special credits or explanations that the icon needs. Please check to see if there's a footnote before you download anything.
If a picture appears transparent on this background, it will display as transparent on LJ—none of the icons have the exact same color as the background of this website. ;)