Just moved, bathroom walls have visible, but not raised, drip marks down the walls. Is it from wallpaper glue not removed properly? How do we prep and repaint?

 

Hard to say without being there to see it. Sometimes water will leave a stain on poor quality paint. In that case, I think you can just paint over it and hide it. Only one way to find out... roll a little paint on it with a weenie roller and let it dry... then you will know.

 

As XSleeper said, it's hard to tell without actually seeing it. However, I had two similar experiences with different causes.
1 - A few weeks after painting a kitchen with 2 coats of paint with primer in it, in a color just slightly warmer than the previous color, shallow drip marks, not from the paint, started to appeared where I know there weren't any liquids splashed or moisture issues. I was told by someone who paints a lot that the cause was most likely due to water marks or oil drips being on the walls previously and since I didn't wipe down ALL the walls with a good cleaner or use a "stain blocking" primer first, the stains leached through.
2 - Could be similar to above or the bathroom was painted and paint did not cure completely. Moisture/Steam from shower settled on walls and discolored paint. Could also be wrong paint was used in bathroom. Bathrooms should be painted with a mold/mildew resistant paint and a finish with some type of sheen. Satin is "OK", but semi-gloss is better. Gloss is best but, not too many people like shiny bathrooms. But gloss is ok for the trim.
In a nutshell, best to use a stain blocking, mold/mildew resistant primer first. Then paint with a mold/mildew resistant satin or semi-gloss paint. Hope this helps, I'm not an expert, just my own experiences.

 

HAHA, had a good chuckle with that one

 

If you can't feel the drips - more paint should be the fix. Painted over wallpaper adhesive generally leaves a rough spot and will often have minor cracking in the paint.