If you use Google+ to store your photos, you're in for a treat.
Google just rolled out a minor Gmail update today that lets you easily attach a Google+ photo from within the composition window. Once you're done writing your email, select the option to insert a photo and it'll default to your Google+ albums, as well as anything you've privately backed up to your Google+ account.
You can also share whole albums with family and friends, and fear not: even if the album is private, only those you've shared the albums with will be able to see them. You can also resize photos right from within the composition window.
The move is another passive ploy on Google's end to get its users hooked on using Google+ to store their photos. If you have Google+ on your Android device or iPhone, you have the option for every photo you take to be backed up to your Google+ account (and set private by default).
Note that this change only affects the Gmail web client, not the mobile app.