Not sure if anyone has done these yet but here are some simple drag actions for images in CSS.
The second one if for dropping between url() so you can use the background snippet for instance then drag an image between the brackets.
Image as a background:
File types:
png, jpg, jpeg, gif
Commands:
echo "background-image: url(\"$TM_DROPPED_FILE\");"
Scope:
meta.property-list.css
Image Path:
File types:
png, jpg, jpeg, gif
Commands
echo -n "\"$TM_DROPPED_FILE\""
meta.property-value.css