How to add tile input to block

how would i go about adding tile / tilemap inputs to a custom block?

You can do it like setCurrentTilemap() block do:
//% tilemap.shadow=tiles_tilemap_editor
in tilemap.ts

     * Sets the given tilemap to be the current active tilemap in the game
     * @param tilemap The tilemap to set as the current tilemap
    //% blockId=set_current_tilemap block="set tilemap to $tilemap"
    //% weight=201 blockGap=8
    //% tilemap.shadow=tiles_tilemap_editor
    //% blockNamespace="scene" group="Tilemaps" duplicateShadowOnDrag
    //% help=tiles/set-current-tilemap
    export function setCurrentTilemap(tilemap: TileMapData) {