So I've noticed a lot of ladies quite desperately asking for their preg test pictures to be "tweaked" by someone else and I feel bad that they don't seem to know how to do it. Any photo editing app should do the trick, and just play with the different filters and light editing tools; increasing the contrast should do the trick. Avery makes a nice free photo app. iPhone has its own image editing built-in and I'm guessing other phones do, too.
Just FYI. :) You can do this yourself way easy!