Ensure the file is at least 300 DPI. If it looks "crunchy" or pixelated on your screen, it will look even worse on your skin.
When searching for tattoo inspiration, the file format matters. A file with a transparent background is superior for several reasons:
Layer the "X" with other elements like skulls, dates, or quotes to create a custom piece. specific art style for this "X," such as hand-drawn or geometric?
If you're looking for X tattoo PNG images, here are some popular sources: