Inside the alley I found myself cornered by unpleasant sights: walls covered with cracks and peeling paint, storm drains clogged with moss, dumpsters overflowing with bags, cans, and rotten trash.
Inside the alley I found myself cornered by unpleasant sights: walls covered with cracks and peeling paint; storm drains clogged with moss; dumpsters overflowing with bags, cans, and rotten trash.
Inside the alley I found myself cornered by unpleasant sights. Walls covered with cracks and peeling paint. Storm drains clogged with moss. Dumpsters overflowing with bags, cans, and rotten trash.
Or maybe the three of them are orthographically correct in their respective contexts?
EDIT (based on dockeryZ's answer):
I think second example is right, regardless of the context. Explanation: http://theoatmeal.com/comics/semicolon.