Images: Size Does Matter
One thing I tell all of my clients is that high quality graphics are the difference between being taken seriously and looking like you do not know what you are talking about. This goes back to that Weird Al grammar lesson - professional credibility is like communication: both verbal and nonverbal. The small things matter and carry a lot of weight.
So, invest your time or money accordingly: either learn to do quality graphics or pay someone to do it. Not a Photoshop wizard? I love picmonkey.com for blogs and other posts with basic graphics. Check it out.
Also, there are scores of freelance graphics designers that do really good work. Not sure? Ask to see samples and speak with their clients to get references. Check out oDesk for people that do work like this.