As far as the number of pages, it will work. How easily it will be to use depends on how you are using your TVs.
For example, if you have sections to your site, and each section has its own header image, you can use an image type TV with the default value of @INHERIT, and no output formatting so it just outputs the raw image filename. Then edit the TV for each top-level parent resource to have the link to the image you want. Now all of the resources in that folder (under that branch of the tree) will inherit their parent's image.
In your template it would look like this:
<style>
.masthead {background: url(../images/[[*imageTV]]) top center no-repeat;}
</style>
Or, it might be easier to have separate .css files for each section, and use the TV to indicate which .css file to use:
<link rel="stylesheet" type="text/css" href="assets/styles/[[*myTV]].css">
In this case, I would be inclined to make it a radio button TV with a button for each .css file, that way the editor only has to click the one he wants. No need to remember what they're all called and type them in!