diff --git a/app/components/attachment/edit_component.rb b/app/components/attachment/edit_component.rb
index 5d8c11612..faee823c4 100644
--- a/app/components/attachment/edit_component.rb
+++ b/app/components/attachment/edit_component.rb
@@ -204,12 +204,14 @@ class Attachment::EditComponent < ApplicationComponent
   end
 
   def allowed_formats
-    return nil unless champ&.titre_identite?
-
     @allowed_formats ||= begin
-                           content_type_validator.options[:in].filter_map do |content_type|
+                           formats = content_type_validator.options[:in].filter_map do |content_type|
                              MiniMime.lookup_by_content_type(content_type)&.extension
                            end.uniq.sort_by { EXTENSIONS_ORDER.index(_1) || 999 }
+
+                           # When too many formats are allowed, consider instead manually indicating
+                           # above the input a more comprehensive of formats allowed, like "any image", or a simplified list.
+                           formats.size > 5 ? [] : formats
                          end
   end
 
diff --git a/app/components/attachment/edit_component/edit_component.html.haml b/app/components/attachment/edit_component/edit_component.html.haml
index 116271c19..d0d88b590 100644
--- a/app/components/attachment/edit_component/edit_component.html.haml
+++ b/app/components/attachment/edit_component/edit_component.html.haml
@@ -23,7 +23,7 @@
     %p.fr-text--sm.fr-text-mention--grey.fr-mb-1w
       - if max_file_size.present?
         = t('.max_file_size', max_file_size: number_to_human_size(max_file_size))
-      - if allowed_formats
+      - if allowed_formats.present?
         = t('.allowed_formats', formats: allowed_formats.join(', '))
 
 
diff --git a/app/views/administrateurs/groupe_instructeurs/_signature.html.haml b/app/views/administrateurs/groupe_instructeurs/_signature.html.haml
index 6abd1ef27..42cfba025 100644
--- a/app/views/administrateurs/groupe_instructeurs/_signature.html.haml
+++ b/app/views/administrateurs/groupe_instructeurs/_signature.html.haml
@@ -1,10 +1,10 @@
 .card.mt-2
   = render NestedForms::FormOwnerComponent.new
-  = form_with url: { action: :add_signature }, method: :post, html: { multipart: true, class: 'form' } do |f|
+  = form_with url: { action: :add_signature }, method: :post, html: { multipart: true } do |f|
     .card-title Tampon de l'attestation
-    = render Attachment::EditComponent.new(attached_file: groupe_instructeur.signature, direct_upload: false)
-    %p.notice
-      Formats acceptés : JPG / JPEG / PNG.
-      %br
-      Dimensions conseillées : au minimum 500 px de largeur ou de hauteur, poids maximum : 0,5 Mo.
     = f.submit 'Ajouter signature', class: 'fr-btn'
+
+    .fr-upload-group.fr-mb-4w
+      %p.fr-text--sm.fr-text-mention--grey.fr-mb-1w
+        Dimensions conseillées : au minimum 500 px de largeur ou de hauteur.
+      = render Attachment::EditComponent.new(attached_file: groupe_instructeur.signature, direct_upload: false)