I suspect that you are not importing the pictures at a reasonable size, else the size of the VI should not increase that much.
For example, if your button is 50x50pixels, don't import a 5 megapixel image. You should resize/resample your image in a photoediting program so it only retains enough information needed for the final size.
Why not use a mouse down event on a picture indicator as a button?? Then you could load whatever image you want into the picture. Or put a transparent button on top of the picture indicator.
You can edit several parts of the Control (text, picture and button), it has hoover capabilities. If you miss anything please leave a message at the Lava Support forum.