Well.. Your in the right forum so thats your first start..
I'd suggest finding a few books about PHP & MySQL..
Ask Hot? (Y/N)
So you want a table like this in MySQL.
int -> Photo
text -> Filename
int -> Score
So you'd display a page like this
mysql_connect( // connetion information);
$res = mysql_query("SELECT * FROM Photos ORDER BY RAND() LIMIT 1");
$row = mysql_fetch_array($res);
$photo = $row["filename"];
$id = $row["ID"];
<img src="<?echo $photo?>"><br>
<a href="vote.php?id=<?echo $id?>&vote=yes">Yes</a>
<a href="vote.php?id=<?echo $id?>&vote=no">No</a>
The vote.php would UPDATE the Photo table score either +1 or -1 depending on the vote. Then you could refernce the table again on who's photo has the highest score etc...
Once you understand the basics of PHP & MySQL the rest is quick and simple... I just wrote this on the fly with some time you could make a very advanced version of this.
BTW... I've been drinking... So please don't tear apart my code.