As this article,I think we want to find all of the Eulerian path.But Mathematica have no such function to do this directly.So I will delete the edge 1 <-> 2
first,then use FindEulerianCycle
like follow:
###Make a intermediate graph without edge
1 <-> 2
:pts = {{0, 0}, {1, 0}, {1, 1}, {0, 1}, {1/2, 1 + Sqrt[3]/2}}; g = EdgeDelete[ g1=Graph[{1 <-> 2, 2 <-> 3, 3 <-> 4, 1 <-> 3, 1 <-> 4, 2 <-> 4, 4 <-> 5, 3 <-> 5}, VertexCoordinates -> pts, VertexLabels -> "Name"], 1 <-> 2]
Find all of the Eulerian path:
paths=Prepend[#, 1 <-> 2] & /@ FindEulerianCycle[g, All]
MapIndexed[
Export[ToString@First[#2] <> ".gif", #, "DisplayDurations" -> 0.5] &,
FoldList[HighlightGraph[#1, #2, GraphHighlightStyle -> "Thick"] &,
g1, #] & /@ paths]
PS: I found the vertex $3$,$4$,$1$ and $4$$2$ is completely equivalent.So you can find another $6$ path.Actually II think this is a bug of FindEulerianCycle
which cannot find another $6$$18$ path at least.(I have reported it to W.R. as CASE:3741151.If I get any useful response,I will update it to here.)