Note: this list is generated by looking for the string for this theme hook, so it may include some references that are not actually using this theme hook.

backdrop_common_theme in core/includes/common.inc
Provides theme registration for themes across .inc files.
contact_form_permissions in core/modules/contact/contact.admin.inc
Builds a matrix of contact permissions.
date_timezone_element_process in core/modules/date/date.elements.inc
Creates a timezone form element.
file_element_info in core/modules/file/file.module
Implements hook_element_info().
filter_format_editor_image_form in core/modules/filter/filter.pages.inc
Form callback: Display a form for inserting/editing an image.
form_pre_render_conditional_form_element in core/includes/form.inc
Adds additional customization to a form element when its title or description is set.
node_type_form_permissions in core/modules/node/node.types.inc
Builds a matrix of node permissions for this node type.
options_element_info in core/modules/field/modules/options/options.module
Implements hook_element_info().
system_element_info in core/modules/system/system.module
Implements hook_element_info().
taxonomy_vocabulary_form_permissions in core/modules/taxonomy/taxonomy.admin.inc
Builds a matrix of node permissions for this node type.
theme_date_popup in core/modules/date/date.theme.inc
Format a date popup element.
theme_date_select in core/modules/date/date.theme.inc
Returns HTML for a "date_select" element, including all child elements.
theme_date_text in core/modules/date/date.theme.inc
Returns HTML for a date text element.
theme_date_timezone in core/modules/date/date.theme.inc
Returns HTML for a date timezone element.
theme_link_field_wrapper in core/modules/link/link.theme.inc
Wraps the link field form element.
views_ui_add_item_form in core/modules/views_ui/views_ui.admin.inc
Form to add_item items in the views UI.
_form_example_element_info in modules/examples/form_example/form_example_elements.inc
Utility function providing data for form_example_element_info().