Get all images from a section I want to get all images from the section projekte which are bound to the asset field bild I then want to fiddle around with .limit() and maybe random filters.

So I grabbed all images like described here

This works but as soon as I add .limit()

{% set projectImg = craft.entries.section('projekte').find() %}
{% set projectImages = [] %}

{% for item in projectImg %}
  {% set currentImage = item.bild %}
  {% set projectImages = projectImages | merge(currentImage) %}
{% endfor %}

{% for asset in projectImages.limit(3) %}
   &lt;img src="{{ asset.url }}"&gt;
{% endfor %}


This results in 


  PHP Notice: Array to string conversion


Why can't I just ad whatever filter I want on that new loop now?
This is a misunderstanding of the difference between an ElementCriteria model and actual fetched elements.

Some useful background reading: 

https://craftcms.com/docs/templating/elementcriteriamodel

What are the differences between an elementCriteriaModel and fetched elements?

You could do what you're looking for using Twig's random method:

{% set projectImg = craft.entries.section('projekte').find() %}
{% set projectImages = [] %}

{% for item in projectImg %}
    {% set currentImage = item.bild %}
    {% set projectImages = projectImages | merge(currentImage) %}
{% endfor %}

{# Grab 3 random images from the array #}
{% for counter in 0..2 %}
    {% set asset = random(projectImages) %}

    &lt;img src="{{ asset.url }}"&gt;
{% endfor %}