Is my friend entitled to a commission (brokerage fee) for helping me see pictures of a motorcycle I bought from his father, especially since he did not stipulate that before the sale, and should I give him the amount he is pleased with, or is there a specific amount for that?

The reference for determining the broker's fee and who is responsible for paying it is the prior agreement; if there is no agreement, then it is the custom. If an agreement and mutual consent are reached contrary to custom, there is no harm. However, if this does not occur, then it is impermissible. There is no fixed percentage for the brokerage fee; rather, whatever is agreed upon is permissible, but it should be within the bounds of common custom. If the seller's son acted as an intermediary and is customarily entitled to a commission, then you must pay it to him, and its amount is determined by custom unless you agree otherwise. However, if he did not act as an intermediary and requested a commission for sending pictures, then if he was a volunteer, he is not entitled to it. But if he stipulated it or if it is customarily due, then he is entitled to a fair wage (ujrat al-mithl). In case of dispute, one should refer to the Sharia judiciary or scholars of knowledge.