Vyberte MYSQL do tohoto týdne

SELECT  *
FROM    images
WHERE   userid = $userid
        AND uploadeddate >= CURDATE() - INTERVAL WEEKDAY(day) DAY
        AND uploadeddate < CURDATE() - INTERVAL WEEKDAY(day) DAY + INTERVAL 7 DAY

Vytvořte index na (userid, uploadeddate) aby to fungovalo rychle.