The limit for more recent versions of Splunk 6.3 and higher is definitely in the tens of thousands. More than a few thousand will be noticeable in terms of the amount of memory a dashboard eats up.
200 should be no issue.
There is no override.
how are you populating the drop down? I have had a dropdown of over 1000, and I am not sure of any limit, though depending on how it is populated, i have noticed lag times in the drop down being populated. Also, what version of Splunk are you using?
Using version 6.5.2 - This is the jist of my query in the dropdown |inputlookup datafile |sort+ app_names|dedup app_names? Any reason I am only get 55 of the 200+ dropdown application names?
when you open the input to edit it in the dashboard and you click "Run Search" do you see 200+ app_names or just 55? is it because of the dedup?
Do this |inputlookup datafile |stats dc(app_names) as unique
and see what number you get
Also, I would change your original query to this: |inputlookup datafile |dedup app_names | sort + app_names