I'm not a designer. I never studied art, although I liked to draw things when I was a kid, like many other kids I suppose. Nevertheless, I guess is fair to say that I like to make things look good. Probably that's what people notices, and when there is something to do that should look good, they sometimes ask me to do that for them.
As I was saying, I'm not a professional or anything. But, of course, there are no professional designers in a lab of CS and EE graduate students. It seems I made things look good enough for being labeled the "official" lab picture-maker. So along my 3+ years in the RESL laboratory, I was asked many times to draw pictures about the IT field we are working on: Wireless Sensor Networks. Of course, pictures must be done with the computer, so a lot of times I basically combined smaller existing pictures to create the concept I was asked. I started just drawing them in MS's Power Point, and then moved to MS's Visio. Microsoft products are good because they have a large database of vector images than can be searched withing the program and modified to fit your requirements. However, Visio files, as all MS Office files, have a proprietary format. Moreover, they don't export properly to SVG (Standard Vector Graphics). When I moved to Linux, I refused to change to Windows every time to use Visio, so I tried to use other programs that could provide me similar results. Software such Dia and Kivio are good to draw vector-based flowcharts and block diagrams, but they are not what I need to make things look good. The answer is general SVG drawing programs (such as Inkscape) combined with online SVG databases, such as the Open Clipart Project (apparently currently moving to a new server). SVG images can look really good, but they are more cumbersome to produce and normally take longer time. However, the SVG format is a true standard that I feel good about using, not like MS proprietary formats.
Many of my early pictures have been lost. Nevertheless, here is a small sample.
By the way, sometimes I do logos too...