I think you splitting your database in such an extensive manner. I think you could get rid of the pictures table, thats one.
Second, include the picture names with either your webpages table (for each record, i'm geussing it is a webpage, so have a column for pictures, and if you have multiple pictures, upon uploading create a string of filenames delimited with a character, say | ) or have them stored in the same way in the categories table.
Now I'm not sure how many pictures you expect to have for each page, if your possibilities are open then the above concept might work better for you, otherwise, if you could restrict the number of pictures per page, say 4 pictures or less, you could probably get away with creating a column for each picture in where ever you want to store the pictures names.
Of course, in your webpages table you should have a column to associate it with a category. Say, cat_id name cat_name. Just so you would know how to relate things together.