Hi Again Ulrich,
Yes, we had made the customisation into the file flowplayer5/admin/class-flowplayer5-taxonomy-meta.php . Only a thought but you might want to add the option to the plugin. I think it’s a very handy addition.
I added this at line 129:
<div class="form-field fp5-select-splash">
<label for="term_meta[fp5-select-splash]"><?php _e( 'Select Splash Image', 'flowplayer5' ); ?></label>
<input class="media-url" type="text" name="term_meta[fp5-select-splash]" id="term_meta[fp5-select-splash]" value="<?php if ( isset ( $term_meta['fp5-select-splash'] ) ) echo esc_attr( $term_meta['fp5-select-splash'] ); ?>" />
<p class="description"><?php _e( 'Background image for playlist', 'flowplayer5' ); ?></p>
</div>
And then this at 168:
<tr class="form-field fp5-select-splash">
<th scope="row" valign="top"><label for="term_meta[fp5-select-splash]"><?php _e( 'Select a splash image', 'flowplayer5' ); ?></label></th>
<td>
<input class="media-url" type="text" name="term_meta[fp5-select-splash]" id="term_meta[fp5-select-splash]" value="<?php if ( isset ( $term_meta['fp5-select-splash'] ) ) echo esc_attr( $term_meta['fp5-select-splash'] ); ?>" />
<p class="description"><?php _e( 'Select a splash image for this playlist', 'flowplayer5' ); ?></p>
</td>
</tr>