There is a line break after inserting of completed.pstpl into the final survey page (final survey page when the survey responses have been saved and the survey is over). This line break can lead to an ugly gap in the template design if specific color combinations are used.
(This issue does not appear while using the template editor, only in the actual survey. Also, it seems to happen with all templates - I have reproduced the issue with the default template, my modification of the default template and the bluengrey template)

According to Marcel Minke, "Limesurvey should NOT create any line break, instead the user should be able to handle that at the template." (see thread for this issue: http://www.limesurvey.org/de/forum/design-issues/92665-template-lbr-g-automatically-inserted-on-final-survey-page-messing-up-design)