Issues with TempDB mdf file ever increasing
So first, why is your data file growth set to 1MB? If you need to accommodate 20MB worth of data in tempdb the file will have to grow 20 individual times! Imagine if you have a query that requires a 200MB or 2GB spill to disk? Yikes.

Growth events are expensive, especially on older SAS/SATA storage and especially if you don't have instant file initialization enabled. You should really try to pre-size your file so that they're big enough to accommodate your busiest workload, and avoid growth events altogether. This isn't always practical, but in lieu of that, the growth size should be much larger. You really want this to be a rare and isolated event, not one that is occurring constantly. What is the point of keeping tempdb small, when it's going to use more space eventually? Are you going to lease the space out temporarily to the highest bidder, then evict them?

Also, why is there only one tempdb file? This is a common source of contention. Typical wisdom suggests to start with 4 files, even if they're all on the same disk. This can drastically reduce contention especially when multiple concurrent processes are trying to create objects or otherwise use space in tempdb. You may also want to look into enabling trace flag 1117 (which ensures that all of your data files grow at the same time) and trace flag 1118 (which changes extent allocation). Links about these below.

None of this will solve your core issue, of course - lack of (or concern over) disk space. If you don't have enough disk space to support the current usage of your system (whether it's the system or your users), get more disk space, or move the system. You might be able to find some of the culprits (see this answer for some common ones), but you won't be able to squash them all. 

You might also find these things useful:


this blog post by Jason Hall
this survey from Paul Randal
this TechNet article on optimizing tempdb
this squashed myth from Paul Randal
this discussion on TF1118
this blog post from Paul White, explaining temporary object caching
this question about determining version store usage
this answer (also linked above) on determining contributors to tempdb log usage, and common causes for tempdb usage in the first place
there are also three "Linked Questions" in the right sidebar of the above answer that may be useful
this documentation on contributors to tempdb size
this question, also about contributors to tempdb size
this tip about tempdb configuration best practices on mssqltips.com


And also, now that we know you are using Service Broker, you may want to read these two pages which might help explain why your conversations aren't clearing out:


http://itknowledgeexchange.techtarget.com/sql-server/writeup-of-a-strange-service-broker-and-tempdb-problem/
http://social.msdn.microsoft.com/Forums/sqlserver/en-US/5c4414a6-213b-4a69-8dcd-f162bc979b3b/service-broker-filling-tempdb?forum=sqlservicebroker