If the images in your flash gallery (really love the pictures, by the way) are really big, that might effect the loading time between going from picture to picture.  Just curious are you selling these photos Online?  If so you might want to use a smaller sample picture for each one to make it load a little faster. 

You could try increasing the framerate. In Flash, use the shortcut: Control + j to bring up the Document Properties. From there, you'll see the framerate as FPS (frames per second). By default, Flash sets this to 12fps. Bump it up to around 26 and Ok the document properties window. Test your movie (Control + Return/Enter) to see the immediate increase in speed.

You might also want to use a graphics editing program like Photoshop or Fireworks to add a watermark to your photos. Flash is very easily decompiled, and your planned source of income could be had for free with just one click. Alternatively, look into some software called SWF Encrypt. This protects your swf files from most decompilers.

Hope that helps