To display a bigger image you can use teh width and height attributes of the img tag, just as you have done in the code presented.
to change the display to more than 12, in the code that gets the records from the database must be limiting it to 12.
The code that you have provided will only display one image, there should be more code than that. you will have to provide teh rest of the code for more help on increasing the number of pictures to display
Unsolved 
