Sensible way to have different number of entries on page one of pagination?
There's an offset parameter that allows you to skip the first entries from your ElementCriteriaModel.

You would set up two nearly identical ElementCriteriaModels, one exclusivly for your featured entry, using the first() method to only query for the first entry, and to the second one you'd add offset(1) as a parameter, to get all the other entries for your pagination.

{% set params = { section: 'blog' } %}

{# Get the featured entry #}
{% set featuredEntry = craft.entries(params).first() %}

{# Get all the other entries #}
{% set entries = craft.entries(params).offset(1).limit(10) %}

{% paginate entries as entriesOnPage %}

    {# Show featured entry on page one #}
    {% if paginate.currentPage == 1 %}
        &lt;img src="{{ featuredEntry.url('fullwidth') }}" class="fullwidth"&gt;
    {% endif %}

    {% for entry in entriesOnPage %}
        &lt;img src="{{ entry.url('thumb') }}" class="thumb"&gt;
    {% endfor %}

{% endpaginate %}