Your images are probably stored on your SD card to begin with. You could use something like Dropbox to back them up (this can be done automatically, I believe, though I don't do so myself), or just copy them to a computer every now and then.
If you store your contacts as Google contacts and allow contact syncing they will be backed up to your GMail account. You can easily check: log in to your GMail from a browser, click on the red word "GMail" and select "Contacts". Are they there?
If you don't want to save them to Google's cloud, I believe you can use software like MyPhoneExplorer (Windows) to sync or back up stuff. Or there's always the manual approach: in your contacts app select the import/export option (or similar - it's almost 2 years since I used Sense, so don't remember whether HTC messed with menu item names), and export your address book to SD. This will produce a vcard file (.vcf) which you can copy somewhere safe.