  New optical narrowband imaging observations of the fields of several ULXs are
presented. Known supershell nebulae are associated with a number of these ULXs,
which we detect in emission line filters such as [S II], He II, [O II] and [O
III]. New nebulae are discovered, which are candidate ULX-powered supershells.
The morphologies and emission line fluxes of these nebulae could then be used
to infer the properties of the emitting gas, which gives clues to the
energizing source (photoionization and/or shock-excitation, both possibly from
the ULX). Studies of supershells powered by ULXs can help to constrain the
nature of ULXs themselves, such as the isotropy of the X-ray emission and the
strength of their outflows.
