To send pictures on TikTok via direct messages, open TikTok, go to the Inbox section, select a chat with a friend, then tap the gallery or plus icon to choose and send photos from your phone's gallery. You can select and send one or multiple photos this way within the chat interface. If you want to share a photo as a TikTok post privately, you can upload the photo as a video post, set its visibility to only yourself or friends, and then share that post link via message.

Steps to send pictures in TikTok messages:

• Open TikTok and tap on Inbox.
• Select an existing chat or start a new one.
• Tap the plus icon or gallery icon in the message bar.
• Choose the photo(s) you want to send from your device's gallery.
• Tap send to share the photo(s) with the recipient.

Alternative method to share photos:

• Upload a photo as a TikTok post.
• Set post visibility to private or friends only.
• After the post is live, tap the three dots and use the share option.
• Send the post to your friend via TikTok messages.

This process works for both iPhone and Android devices, and TikTok messaging supports photo sharing directly in chats as of recent updates.