At this point, the general shape of the face is set, but there can be more detail added. Keep in mind that with 3D printing, there is such a thing as too much detail, since some of it won't come through. Then again, details tend to be the most impressive part, so spending some time sharpening some edges may be of benefit. Here's how:
The Crease tool is great for adding small details such as lines or ridges to the model and can really give your design some style. But use caution—additive creases can create undesired ridges if overused. Be sure to adjust your view to make sure that isn't happening. If it does, remember that you can undo or smooth quickly without switching brushes by holding down Shift while drawing at any time as well. If elements aren't where you want them, the Grab brush (G) will allow you to reposition things to a certain degree.
For the next steps, we'll be using the Object Mode tools, so after sculpting is done, switch back to Object Mode and click on the Sculpt Mode dropdown in the menu of the 3D View and select Object Mode:
Here is a handy guide for easy reference to some of the keyboard shortcuts used in sculpt mode. For a complete set of shortcuts, be sure to check the Blender manual online.