We had an "arty party" for DD1's fifth.
We did use Baker Ross, so these might not suit you, but here's what we did anyway:
Decorate your own mug (not the glass painting ones, but the ones where you just draw a picture on a bit of paper and slot it into a plastic mug)
Decorate your own badge (similar - circles of paper which you decorate and put in a clip-together badge case).
Foam sun visors, decorated with self-adhesive foam letters and shapes.
Colour-in flying bugs (like model planes, but bug shaped).
Those were all from the catalogue - sorry haven't got time to find pages.
We also provided a fairy cake per child and a load of icing and cake decorating stuff, so they could decorate their own cake, which they had with their tea.
Of the above, the DIY mugs, hats and badges were a hit - the flying bugs less so, but they were REALLY cheap!! The cakes were definitely the most exciting - and also the easiest from my point of view.
Be warned, you do need a decent range of things to do. Some of them finish a craft like lightening, while others will spend all afternoon painstakingly decorating one item.