I remember that someone used to make a retexture mod for the PipBoy 3000 in Fallout 3. What that modder did was that he included a small photograph of Amata's face tucked to the left side of the PipBoy. Impressive work of art I must say. Well, since Fallout NV has many of the same assets as Fallout 3, it also works for Fallout NV. I discovered this...accidentally. It's just files that replace the textures for the PipBoy 3000, that's all it is. No ESM or ESP, just a directory of DDS files.
This gave me an idea. I created a custom PipBoy texture with a photograph of Sarah Lyons. There are two images attached to this thread showing you what I did. My character was in the Pitt, so what you see is a field test. The retexture affects only your character's PipBoy. Anyone else wearing a PipBoy does not have the photo. For example, I looked at Butch's PipBoy, and the texture for his is still the default texture.
I'm not good at lifelike or realistic textures. So, despite how it looks, I hope there are some who still give me credit for this. It wasn't easy to do, trying to not get Sarah's image to conflict with the base texture. If anyone likes what they see, I can make the textures downloadable for others to try out.
What's the reason for Sarah Lyons' face being on the PipBoy? Well, I'm glad you asked. From what I learned in Fallout 4, Sarah Lyons became the new Brotherhood of Steel elder after her father's death. This new position of hers did not last long because she too had died soon afterwards. Now, what would cause the Lone Wanderer to disappear from the Capital Wasteland? He or she has a photo of Sarah, which would indicate that there was a relationship, either as friends or as lovers. Could her death have taken a toll on the Wanderer?