Hi,
I am new to Silverstripe and need some help. How do I customize themes like change theme image, site color, etc...Is there a program I could use as I don't know any programming. I am trying to build a photo gallery; is there themes for this?

Thanks.

Delayed reply but:

There is no program you can just use to change the colours and pictures, although you could just install a theme:
http://www.silverstripe.org/themes

If you know css and html you can play around with the css and ss files to alter images and site colours.

If you don't know html and css I recommend these tutorials:
http://www.w3schools.com/html/default.asp
http://www.w3schools.com/css/default.asp

Also it might be worth having a read of the Silverstripe tutorials to gain an understanding of how stuff works, even if you have no intention of programming:
http://doc.silverstripe.org/tutorials

If you want an Image-Gallery there is a module that you can just plug in and go, although you need to install 2 other modules before it for it to work:
http://www.silverstripe.org/dataobjectmanager-module/
http://www.silverstripe.org/swfuploadfield-module/
http://www.silverstripe.org/imagegallery-module/

Good luck