I have been learning front end development off and on for quite a while now. I feel like I have a pretty good grasp on the concept. I know the best way to really learn this is to put it into practice. That's where I'm getting stuck. I feel in order to really dive into learning this sort of stuff I need to start making websites. Obviously I don't believe I'm anywhere near good enough to start doing this for clients and am wondering if there are any sites or sources out there that already have image assets to use in order to piece mock up sites together in order to really learn this. I'm not the best at the part of creating assets through photoshop is why I ask.

Any suggestions? I would really appreciate it!
Thanks!