you can change the icons to use "default server stuff" - check at the delivered XML files a pick a button at your choice - this makes the buttons visibile without having the icons installed on the client.
e.g.
<button depth="3" name="btnStashAll" style="icon30px, press, hover" pivot="center" pos="281,-21" sprite="ui_game_symbol_hand" defaultcolor="[yellow]" tooltip_key="lblStashAll" sound="[paging_click]" visible="{lootingorvehiclestorage}" />
<button depth="3" name="btnStashFillStacks" style="icon30px, press, hover" pivot="center" pos="317,-21" sprite="ui_game_symbol_loot_sack" defaultcolor="[green]" tooltip_key="lblStashFillStacks" sound="[paging_click]" visible="{lootingorvehiclestorage}" />
<button depth="3" name="btnStashSmart" style="icon30px, press, hover" pivot="center" pos="353,-21" sprite="ui_game_symbol_add" defaultcolor="[red]" tooltip_key="lblStashSmart" sound="[paging_click]" visible="{lootingorvehiclestorage}" />
check: sprite="###" and defaultcolor="###" tags. This is just a mockup - but working