I also had a look for any details - no sign of a probable baptism for Sarah, which is not that unsual. There's good coverage of most of the Dublin City Catholic and Church of Ireland parishes on the free IrishGenealogy website and also Images of the Catholic records on the NLI website. It's quite common to see cases where baptism records for one or more children to a couple cannot be located - the priest may have fogotten to note the details in the register, apparently in busy parishes they kept their own notes with the intention to add to the main register later, the page the details were entered on may have faded been damaged, or the parish may not have been keeping good records at the time.
I did locate a marriage for James Walsh and Anne King in 1811 in St. Mary's RC which fits the timeline, and several possible children to the couple baptised in the same parish e.g. Anne 1816 Mary Anne 1825 Anne 1825 Christopher 1826... unfortunately the registers for St. Mary's during this timeframe often do not include mother's maiden name, so there's no way to be certain which, if any, of these are siblings to your Sarah. The last of the baptisms I mentioned is the most promising as one of the godparents (sponsors) is a "Bartel" (Bartholomew) King.. so could be related to Anne.
The Pro-Cathedral, which is the main church for the parish started construction just a few years after James and Anne married, before that time buildings in several locations were used, including a previous parish church on Liffey street.
James and Sarah look reasonably well off in the photo you've added and the database I have on Photographers and places the business at that address (140 Stephen's green West) in the early 1880s - so there should be civil death certs available for them. The images of civil death records on IrishGenealogy only cover from the 1890s at the moment, but earlier records will be added in time. As Roger mentioned Walsh is a common surname (4th most common surname in the 1890s) so there would be quite a few James and Anne's to check, but maybe one might show up with an occupation of Coachman... given that they seem to be Catholic they would most likely have been buried in Prospect/Glasnevin cemetery which has very good records, and full details of a family plot could give you useful details. I would suggest trying to locate a death cert first in civil records to narrow down the date, while the basic search on the Glasnevin website is free, you need to buy credits to see the full details.
