diff --git a/CHANGELOG.md b/CHANGELOG.md
index 95931f7..8f0e938 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,12 +6,11 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 ### TODO
-- check if name is valid in admin settings
-- explain things in admin settings
 - compat jpg
 ### Added
 - file description field
 - 'destination' readonly field indicating full save path
+- admin setting section to add extra symbols
 
 ### Changed
 - keep time information in loaded tracks/routes/waypoints, written in saved files
diff --git a/controller/utilscontroller.php b/controller/utilscontroller.php
index fc86461..29178b7 100644
--- a/controller/utilscontroller.php
+++ b/controller/utilscontroller.php
@@ -143,6 +143,18 @@ class UtilsController extends Controller {
     public function uploadExtraSymbol($addExtraSymbolName) {
 		$newSymbol = $this->request->getUploadedFile('uploadsymbol');
 		$filename = str_replace(array('../', '..\\', '/'), '', $addExtraSymbolName);
+        if (!endswith($newSymbol['name'], '.png')){
+            return new DataResponse(
+                [
+                    'data' =>
+                    [
+                        'message' => 'File has to be a png'
+                    ],
+                    'status' => 'fail'
+                ],
+                Http::STATUS_UNPROCESSABLE_ENTITY
+            );
+        }
         if (empty($newSymbol)) {
             return new DataResponse(
                 [
diff --git a/css/admin.css b/css/admin.css
index 40d4f44..d05c5f0 100644
--- a/css/admin.css
+++ b/css/admin.css
@@ -2,6 +2,9 @@ button#addExtraSymbol{
     width: 33px;
     height: 33px;
 }
+table#extraSymbolsTable{
+    width: 330px;
+}
 table#extraSymbolsTable td{
     text-align: center !important;
 }
diff --git a/js/admin.js b/js/admin.js
index 9cf933f..8a6702c 100644
--- a/js/admin.js
+++ b/js/admin.js
@@ -41,8 +41,6 @@ $(document).ready(function() {
         pasteZone: null,
         dropZone: null,
         done: function (e, response) {
-            //preview('logoMime', response.result.data.name);
-            //alert('success '+response.result.data.name);
             addLogoLine(response.result.data.name);
             OC.msg.finishedSaving('#extraSymbolsSettingsMsg', response.result);
             $('label#uploadsymbol').addClass('icon-upload').removeClass('icon-loading-small');
@@ -50,12 +48,14 @@ $(document).ready(function() {
         submit: function(e, response) {
             OC.msg.startSaving('#extraSymbolsSettingsMsg');
             $('label#uploadsymbol').removeClass('icon-upload').addClass('icon-loading-small');
-            //alert(Object.keys(e.target));
-            //alert('submit '+e.target);
+            if ($('input#addExtraSymbolName').val() === ''){
+                OC.msg.finishedError('#extraSymbolsSettingsMsg', 'Empty symbol name');
+                e.preventDefault();
+                $('label#uploadsymbol').addClass('icon-upload').removeClass('icon-loading-small');
+            }
         },
         fail: function (e, response){
-            //alert('fail '+Object.keys(response));
-            OC.msg.finishedError('#extraSymbolsSettingsMsg', 'failed');
+            OC.msg.finishedError('#extraSymbolsSettingsMsg', response._response.jqXHR.responseJSON.data.message);
             $('label#uploadsymbol').addClass('icon-upload').removeClass('icon-loading-small');
         }
     };
diff --git a/templates/admin.php b/templates/admin.php
index 6f7775b..ab419f9 100644
--- a/templates/admin.php
+++ b/templates/admin.php
@@ -5,7 +5,9 @@ OCP\Util::addstyle('gpxedit', 'admin');
 
     <div class="section" id="gpxedit">
         <h2><?php p($l->t('GpxEdit additional settings')); ?></h2>
-        <label><?php p($l->t( 'Extra symbols' )); ?> </label>
+        <h3><?php p($l->t('Extra symbols')); ?> </h3>
+        <label><?php p($l->t('Those symbols will be available in GpxEdit.')); ?></label><br/>
+        <label><?php p($l->t('Keep in mind that only symbol names are saved in the gpx files. Other programs will display default symbol if they do not know a symbol name.')); ?></label><br/>
         <br />
 		<div id="extraSymbols">
         <table id="extraSymbolsTable">
@@ -28,8 +30,9 @@ OCP\Util::addstyle('gpxedit', 'admin');
 		?>
         </table>
 		</div>
-		<!--button id="addExtraSymbol" class="inlineblock button icon-upload" title="Upload new symbol image"></button-->
 
+        <label><?php p($l->t('Recommended image ratio : 1:1')); ?></label><br/>
+        <label><?php p($l->t('Recommended image resolution : between 24x24 and 50x50')); ?></label><br/>
 		<form class="uploadButton" method="post" action="<?php p($_['uploadPath']) ?>">
             <label for="addExtraSymbolName">New symbol name :</label>
             <input type="text" name="addExtraSymbolName" id="addExtraSymbolName"></input>