Next time you get an email with an image attachment on Gmail, you may find a new option that gives you another way to save the file. The new "Save to Photos" feature will let you save images directly to Google Photos from your Gmail account. No need to manually download files first before saving them to Google's image storage service, though the capability is only available for JPEG attachments at the moment.
While previewing an attachment, you'll find the new option on the upper right-hand corner menu. But if you don't even want to bother previewing the file, you can find the feature as a button on the attachment right next to the "Add to Drive" button. Save to Photos has started rolling out to all Gmail users, including those who only have personal accounts. It's a gradual rollout that will take 15 days to complete, so it may take some time before you get it.
If you already have access to the feature, you have a few days left to save as many files as you want to Google Photos before the service stops offering free unlimited storage. After June 1st, any photo or video you upload will count towards a 15GB limit that's shared with your Gmail, Workspace documents, slides and spreadsheets. You'll have to pay for additional storage going forward, unless you have a Pixel device.