It also queues messages, increasing reliability whilst offline. Rather than not sending, they are stored and sent when the network reappears.
Also built into Nimbuzz is N-World, a centre that allows you to send "gifts" and play games with your contacts.
If Nimbuzz isn't what you are after, why not try GroupMe. Although now part of the Skype family, GroupMe allows you to contact people via Push or SMS, sending both text and photo messages.
IM+ (Free, Paid for version available)
One of our favourite messaging apps no matter what OS, IM+ is a social account aggregator allowing you to connect to users across all your favourite social networking sites, be it Skype, Facebook, Google, Yahoo and more.
IM+ features the ability to messages and photos, as well as group messaging in Skype AIM and ICQ. Personal status messages can be created too, to share what you're doing across all platforms.
The Windows Phone app is not as well stocked as on other OS', but new features are being added all the time, so we're hopeful that things will keep getting better.
If IM+ doesn't provide all the account aggregation that you need, eBuddy Lite Messenger can also be grabbed from the Windows Phone Store. It too provides connection to many different services, like Facebook and Google.
Rounding out our list of Windows messaging apps is Kik, yet another cross OS app that is both simple to use and comes with a variety of features.
Kik connects via a username, thereby protecting personal data like your mobile number and your email address secret. This makes it a very private app, meaning that spam messages are kept to a minimum
Pictures and text can be sent to individuals, with group messaging also being supported. Kik, like many other apps mentioned is also completely free, as messages are sent via the mobile web, or Wi-Fi, rather than via your bundled messages.
Kik might not quite be your thing, so maybe check out KakaoTalk. Although not quite as private - it connects via your mobile number - it does provide free messaging, photo messaging, video and audio to individuals and groups.