Kathmandu International Airport now has computer visa processing stations in the immigration room which will take your picture for the visa, so technically you shouldn't need one. There is also the option of filling out the information and uploading a picture online before you arrive at: https://online.nepalimmigration.gov.np/
However, I would recommend you still bring some hard copy passport pictures. If there is a really long line for the stations, then you can fill it out by paper and use the photos you have. A passport photo is also required to purchase a local sim card, which are very inexpensive. Basically, it doesn't hurt to have some and they don't need to be fancy, just take a selfie against a white wall and print them out at passport photo size.