If you can zoom into your desired altitude (or maybe a little lower) and the textures look good, you should be able to take a screenshot, clip out your areas from that screenshot, and then paste them into the graphics program of your choice. One area to watch out for is the Google watermarks. You shouldn't need huge patches of texture to get things started.

One other way to get what appears to be higher-resolution data is to appear to synthesize higher-resolution data. Take the lower-resolution data, rescale it so that it appears to be higher-resolution data and then blend that higher-resolution data onto the lower-resolution data (ideally in places that aren't on the screen). You can do this as a static one-time operation or you might be able to do it on the fly by compositing color and shading information separately (separate out the hue and saturation channels in one image, then separate out the value channel to another; use higher-resolution value channels to get the appearance of more detail without huge amounts of color noise).