Just be aware, all you actually need is black on transparent headers. You can use the text image command and if someone changes from a black background to white, it’ll reverse the colour of the text. If you can’t get them made, they’re actually pretty simple. There’s a thread on it somewhere RETowers put up at one point I think.
If your budget is really low, I’d also suggest looking at deviantart or if it’s still too low, consider buying a good stock image which can be done relatively cheaply, or try free sites (make sure you adhere to any conditions) in places like wikimedia or pixabay.
