Add label to southeast corner:

convert -font Verdana-Regular -pointsize 9 -background '#00000080' \
 -fill lightblue label:'schutt.org' miff:- | composite -gravity southeast \
 -geometry +0+0 - in.png  out.png

Add text to bottom:

montage -geometry +0+0 -font Verdana-Regular -pointsize 9 \
 -background 'gray(20%)' -fill skyblue \
 -label "Some text goes here" in.png out.png