Some vector is in use in when I'm in Photoshop Elements, basic shapes and text. Many of the graphics I use are coloring book pages I got from the web and colored. They are usually the only ones large enough to look good when printed out. They are in either .jpg or .gif format.
I'm interested in Abobe Illustrator but the $600 price tag is prohibitive for what I do. If I was getting more pro work (get maybe 1 job a month and that's usually for a local non-profit) I'd probably buy it and or Photoshop.
BTW your graphics look GREAT and makes me wish I had an extra $600 hanging around to buy the program!
Even when most of your work is done in Photoshop (Elements) starting with vector art is preferable since you are able to create your raster art at just the size you need it, and you'll have control over how the rendering is done (anti-aliasing or hard edges). Not to mention that the file size is miniscule. But yes, I certainly understand the difficulty in getting into a $600 package. I just recently decided to get back into graphics work and gave up my PC, dropped $1500 on a new (basic) Mac. Add the $1600 for Adobe Creative Suite and you are into some serious money! If I were in your place, I would keep an eye out at garage sales and thrift stores. I have bought older versions of both Illustrator and Photoshop for less than $20 at garage sales. Frankly, anything after Photoshop 3 is worth picking up (5 or later is even better, editable type) and really Illustrator 88 and later are worth having (though if you are on Windows you may not want a pre-7 version). You can get some good deals on eBay too, you just need to be careful that you are getting the full product (not an upgrade) and not a pirated copy. If it comes with the box and manuals, it's probably a full license original. Oh, and if you're on an Intel Mac, you need to be careful about older software, most pre-OSX stuff wont run... found that out the hard way!
It is really surprising how few of the fundamentals of the programs have changed over time. I have been away from them for 8 years (3 full versions) and am finding that old quickeys I would have thought I'd long forgotten fly magically from my fingertips and, even more magically, still work in the new programs! Sure, there are lots of new bells and whistles to learn, but most of the old workflows still flow. Anyway, I hope you find a way to get yourself into Illustrator, even if it's an old version, and take your first steps into a larger world (sorry, couldn't resist the Star Wars quote)!
Oh, and thanks for the compliments on the artwork!