In this work, the effect of adding Se, Te, In, Cs, Y to gallium lanthanum sulphide glass was studied. Structural modifications to the glassy network were achieved by substitution of sulphur, gallium or lanthanum using a melt-quench method in an inert atmosphere. Optical, thermal and mechanical characterisation of the samples revealed tailorable features according to the nature and the amount of glass modifier. In particular, the addition of selenium and tellurium resulted in an extended transmission in the infrared up to 12 μm. Furthermore, for small amounts of selenium, the position of the bandgap did not change significantly, maintaining visible transmission. The addition of indium led to the formation of glasses with longer transmission in the infrared and a cut-off edge around 600nm in the UV-visible range. Over-all, the addition of these modifiers resulted in stronger materials with improved thermal stability and similar mechanical properties to original Ga-La-S glass. The outcome of this work aims to bring a new family of chalcogenide glasses for applications in the infrared and visible range.