Hi there! I can understand how frustrating it must be to not be able to send pictures to your friends. Let's work through this together.

Since you mentioned that your Wi-Fi is working well, the issue may relate to the multimedia messaging service (MMS) settings on your device. On many devices, MMS messages require mobile data to be enabled, even if you're connected to Wi-Fi.

Here are some steps you can follow to potentially resolve this issue:

1. Check Mobile Data Settings:
- Go to System Preferences on your Mac.
- Navigate to Network, and ensure your mobile data (if applicable) is turned on.

2. Verify MMS Settings:
- While the exact steps might vary by application, open the messaging app you are using (like iMessage or any other).
- Check if there are settings related to MMS; make sure it's enabled.

3. Send Through iMessage:
- If you're using iMessage (and you and your friends are both using iPhones), you might want to try sending the pictures via iMessage instead of SMS/MMS. iMessage uses internet data and should work fine.

4. Restart Your Device:
- Sometimes a simple restart can fix connectivity issues. Give it a try to see if that helps.

5. Check for Updates:
- Ensure your Mac is up to date with the latest OS X updates, as software updates can fix bugs that affect connectivity.

If these steps don't resolve the issue, could you provide more details regarding the messaging app you are using and whether you’ve noticed any specific patterns, like if the problem persists over certain networks or only with specific contacts? This information will help me assist you further.

Are you satisfied with the solutions provided so far, or do you want to explore more options?