update preview image

Author: Robin Duda

README.md

@@ -2,7 +2,7 @@
 
 Parses XLSX/XLS/CSV files into ElasticSearch using column titles from a specified row combined with data in columns on each row. May be used with Kibana or other visualization applications, example result using a transaction log in excel format  [image](https://raw.githubusercontent.com/codingchili/parser-banktrans-es/master/sample-redacted.png). The application comes with a web-interface to simplify uploading.
 
-![sample UI image](https://raw.githubusercontent.com/codingchili/parser-excel-elasticsearch/master/excelastic.jpg)
+![sample UI image](https://raw.githubusercontent.com/codingchili/parser-excel-elasticsearch/master/excelastic.png)
 
 ## Features
 - import excel (.xlsx/.xls) files into ElasticSearch.