Is it possible to customize spark? like the picture that displays above the login text boxes?
I assume that you want to read the “Spark End User License Agreement” before posting such questions. I will not, and will not permit others to … decompile, … modify, or create derivative works from the Licensed Products.
Exchangeable icons would be nice (the Free To Chat icon has imho a very poor design) but removing or exchanging the login logo sounds like piracy to me.
http://www.jivesoftware.com/services.jsp may help you to customize Spark, it is possible at nearly no cost.