I'm not a graphic designer per se, but I think I can give you a hand nonetheless. If I'm not wrong, these are just pictures or text on top of a pattern?
You've got pretty much unlimited options.
On the free end, there's the G.I.M.P. (Gnu Image Manipulation Program, not that you need to know in particular). Like I said, it doesn't cost a cent, but it's fairly difficult to use, especially for a beginner, so I wouldn't recommend it.
There are some great options for under $100 that give you a lot of features.
Acorn is around $50 and is super easy to use. I haven't used it a whole lot myself, but I've heard great things about it.
Climbing the price ladder to $60, you find yourself at
Pixelmator. I used it as a holdover while Photoshop didn't agree with my computer, and I was blown away. It's got loads of functionality and a very simple interface to pick up.
Photoshop Elements is at the top end of the sub-$100 programs ($80). It's the little brother of Photoshop, and maintains a lot of the functionality. It does come with a bit of a hefty price tag though (at least for what you've described), but if you plan on doing anything else like this in the future, it might be a good investment.
Any of these options should get the job done, and all of them come with free trials so you can test each out (or do your project if you don't want to pay
). I'm sure they can also be had for cheaper on Amazon or elsewhere, so do a quick Google before clicking Buy.
My personal recommendation would be Pixelmator; it's the perfect blend of price and performance, and it's a ton of fun.
Hope this is helpful, and feel free to PM me or post in the forums again if you need any help with the project itself.