"Bumping" only applies to categories that are sorted via "bump". This means that when a reply is posted, it will push it to appear first.
In /keyword/ mode, images are always sequential, so the bump setting doesn't apply when viewed there. Note however that it can have an affect in other views, which is why it may appear not to make much sense.
I removed the tripcode you mentioned because others can delete your post if they know the tripcode. You should treat it like a password.
>>36 Name: Ben
<mNd/G/T6Km> 2005-01-21 15:29:21 UTCDelete »